Mobile growth has its own vocabulary, and the terms get thrown around loosely. Here's a plain-English glossary of the metrics that actually drive decisions, and how they connect.
Acquisition
- Impressions — times your ad or store listing was shown.
- Installs — app downloads that completed. The top of the mobile funnel.
- Install attribution — the (probabilistic, on iOS) answer to "which campaign drove this install."
- CPI (cost per install) — ad spend ÷ installs. The headline acquisition cost.
Activation & engagement
- Session — a single use of the app.
session_startedis your heartbeat. - Activation — the moment a new user reaches first value (e.g. completed signup or onboarding). The bridge between "installed" and "actually using it."
- DAU / MAU — daily / monthly active users. Their ratio (DAU/MAU) is a rough stickiness measure.
Retention
- Retention rate — the percentage of users who come back on day 1, 7, 30. The single best early signal of product-market fit. Acquisition is wasted if retention is weak.
Monetization
- Conversion to paid — share of users who start a trial or subscription.
- ARPU / ARPPU — average revenue per user / per paying user.
- LTV (lifetime value) — total revenue you expect from a user over time.
- ROAS (return on ad spend) — revenue generated ÷ ad spend. ROAS above 1 means a campaign earns back more than it costs. This is the number that tells you whether to scale a channel.
How they connect
The chain is: spend → installs (CPI) → activation → retention → revenue (LTV) → ROAS. A campaign with cheap installs but poor retention produces low LTV and bad ROAS — so cheap installs aren't automatically good. Watching the whole chain, not just CPI, is what separates profitable growth from burning budget.