Learn · Glossary
Growth terms, defined.
A glossary of the vocabulary behind customer engagement and growth, in plain language. Each entry defines one term in under a minute — deliverability, segmentation, lifecycle metrics, open-source licensing, AI growth teams — and points to the guide that goes deeper.
In this guide
- 01Suppression listA suppression list is a do-not-contact list — unsubscribed addresses, hard bounces, and spam complainers — that an email platform checks before every send. Anyone on the list is silently excluded, regardless of which segment or campaign targets them. It protects sender reputation and is how opt-out requests get honored automatically.Read
- 02Double opt-inDouble opt-in is a two-step email signup: a person submits their address, then clicks a confirmation link sent to that address before they can be mailed. The click proves the address is real and belongs to them. It trades a little signup friction for a cleaner list and stronger consent evidence.Read
- 03Email authenticationEmail authentication is the set of DNS-based standards — SPF, DKIM, and DMARC — that lets receiving mail servers verify a message was really sent by the domain it claims. SPF authorizes sending servers, DKIM signs message content, and DMARC tells receivers what to do when both checks fail. It proves identity; it does not guarantee inbox placement.Read
- 04Email bounceAn email bounce is a delivery failure reported by the receiving mail server: the message was rejected and returned instead of reaching the inbox. Bounces are either hard (permanent, such as a nonexistent address) or soft (temporary, such as a full mailbox). Your bounce rate is a signal mailbox providers use to judge sender reputation.Read
- 05In-app messageAn in-app message is a message displayed inside your product — as a banner, modal, slideout, or tooltip — while the user is actively using it. It requires no separate opt-in, lives only for the session, and cannot reach the user once they leave. That constraint is what separates it from web push and email.Read
- 06Web push notificationA web push notification is a message delivered by the browser through the Push API and a service worker, after the user grants explicit permission. It reaches people when they are not on your site — no app install and no email address required. On iOS, it only works for web apps added to the Home Screen (Safari 16.4+).Read
- 07WebhookA webhook is an HTTP callback: one system sends an automatic POST request to a URL you control the moment a chosen event happens, rather than waiting for you to ask. It is push, not poll — the source pushes data as events occur, so your endpoint receives them within seconds instead of polling on a timer.Read
- 08Dynamic segmentA dynamic segment is an audience defined by rules rather than a fixed list — for example, users who started a trial in the last 14 days and have not yet invited a teammate. As new events arrive, the platform recomputes membership continuously: people enter the moment they match the rules and leave the moment they stop.Read
- 09Lifecycle stageA lifecycle stage is the position a customer occupies in their relationship with your product — for example lead, activated, active, at-risk, or churned. Stages describe how far someone has progressed, so teams can send stage-appropriate messages, build stage-based segments, and measure movement between stages instead of treating every user the same.Read
- 10Tracking planA tracking plan is the living specification of every analytics event a product instruments: each event's name, its properties, when it fires, and who owns it. It is the contract between the people who ship code and the people who read the data, so the same behavior is always recorded the same way.Read
- 11Cohort analysisCohort analysis is the practice of grouping users by a shared starting point — usually signup week or month — and tracking each group's behavior over time. Because every cohort is measured from its own day zero, it separates real changes in retention from mix effects caused by growth or seasonality.Read
- 12Activation rateActivation rate is the percentage of new signups who reach first value — the aha moment — within a defined window. It measures how well a product turns created accounts into users who experience its core benefit. The activation event is product-specific: pick the action most correlated with long-term retention, not the easiest one to hit.Read
- 13Churn rateChurn rate is the share of customers, or revenue, a business loses over a given period, usually a month or a year. It is the inverse of retention: a 5% monthly churn rate means 5% of the customers you started the month with cancelled before it ended.Read
- 14Drip campaignA drip campaign is a fixed, time-based sequence of emails sent in a set order on a set schedule — day 0, day 3, day 7 — regardless of what the recipient does. Every subscriber gets the same messages at the same intervals. It is the simplest form of email automation, and the usual starting point before behavior-triggered journeys.Read
- 15Win-back campaignA win-back campaign is a message sequence sent to lapsed or churned customers to bring them back. It typically opens with a light re-engagement nudge, follows with a what-changed update or an offer, and ends with a final goodbye. Contacts who stay silent are suppressed to protect deliverability.Read
- 16Holdout groupA holdout group is a randomly selected portion of your audience that is deliberately excluded from a campaign or journey so you can measure its true incremental effect. If the holdout converts at the same rate as recipients, the campaign did nothing — those users would have converted anyway.Read
- 17Ideal customer profile (ICP)An ideal customer profile (ICP) is a description of the type of company or account that gets the most value from your product the fastest and stays the longest. It combines firmographics — industry, size, region — with behaviors and pains, and it defines fit at the account level, not the individual.Read
- 18AGPL licenseThe AGPL (GNU Affero General Public License, version 3) is a strong copyleft free-software license published by the Free Software Foundation. Like the GPL, it requires derivative works to stay open under the same terms — but it adds a network-use clause: anyone who interacts with a modified copy over a network must be offered its source code.Read
- 19Multi-tenancyMulti-tenancy is a software architecture where one deployment serves multiple customers — called tenants — from shared infrastructure while keeping each tenant's data logically isolated. A single application instance, database, and codebase handle many organizations at once, with a tenant identifier separating one customer's records from the next.Read
- 20Audit logAn audit log is an append-only, timestamped record of who did what, when — and, ideally, why. Every meaningful action in a system becomes one entry: a message sent, a consent changed, a setting edited, an agent's decision. Because entries are only ever added, never edited, the log is the evidence of what actually happened.Read
- 21Consent recordA consent record is the stored proof that a specific person agreed to a specific data-processing purpose — capturing who consented, when, how, the exact wording they saw, and any later withdrawal. GDPR Article 7(1) makes it the controller's job to demonstrate consent, so without the record, the consent legally does not count.Read
- 22Data residencyData residency is the physical location where data is stored — the country or jurisdiction of the servers that hold it. It determines which local laws can reach the data and which contractual promises a vendor can make. Residency is often confused with sovereignty, localization, and GDPR compliance; it is none of these by itself.Read
- 23Agent orchestrationAgent orchestration is the coordination of multiple AI agents working on shared tasks: routing work to the right agent, handing off context between steps, preventing two agents from editing the same resource, and logging every decision for human review. It is what turns a set of individual agents into a system that can be trusted with real work.Read
- 24Truth PackA Truth Pack is fromHello's name for the shared context document every AI agent works from — your ideal customer profile, brand voice, goals, and product facts. Instead of re-briefing each agent per task, the team edits one document; all eight specialists read it, so their output stays consistent.Read
Related comparisons
- fromHello vs BrazeEnterprise-grade orchestration without the enterprise contract — or the team to run it.
- fromHello vs OneSignalOneSignal's channels, run for you by eight specialists — plus ad-audience sync and open-source self-hosting.
- fromHello vs NovuNovu is the notification infrastructure; fromHello is the growth team that decides what to send.
- fromHello vs KnockKnock is closed notification infrastructure; fromHello is the open-source growth team that decides what to send.
- fromHello vs Customer.ioThe open-source alternative that brings the team, not just the tool.
- fromHello vs MailchimpThe growth engine you graduate to after the newsletter — every channel, run by eight specialists, self-hostable.
- fromHello vs BrevoBrevo's cheap toolkit, plus native ad-audience sync, open-source ownership, and the eight specialists who run growth.
- fromHello vs OrttoOrtto's breadth, but with the eight specialists who run growth and open-source ownership — your data, not Canva's.
- fromHello vs IterableEnterprise cross-channel orchestration — without the sales cycle, the annual contract, or the growth org to run it.
- fromHello vs ListmonkOpen source and self-hostable like Listmonk — but every channel and the eight specialists who run growth, not just a newsletter sender.
- fromHello vs MauticOpen source like Mautic — but with the AI team that runs it, on a modern stack you don't have to maintain.
- fromHello vs DittofeedOpen source, like us — but you still have to run it. We add the eight specialists who do.
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