How GA4 thinks: users, sessions and events
The three building blocks
| Term | What it means | Example |
|---|---|---|
| User | A person (or more precisely a browser or device) visiting your site | Priya on her phone |
| Session | A group of interactions in one visit | Priya's visit on Monday evening |
| Event | A single action | Viewing a page, scrolling, clicking a link, submitting a form |
Everything is an event
Older analytics tools treated page views as the main unit. In GA4, a page view is just one type of event (page_view). A purchase, a sign-up and a video play are events too. This makes GA4 flexible: you can measure almost any action the same way.
Four kinds of events
- Automatically collected: GA4 records these with no setup, such as
page_view,session_startandfirst_visit. - Enhanced measurement: switch-on extras such as scrolls, outbound clicks, site search, video engagement and file downloads.
- Recommended events: names Google suggests for common actions, such as
sign_up,generate_leadandpurchase. - Custom events: your own names for anything else.
Key events: the actions that matter
Most events are just activity. A few show real business results — a lead, a sign-up, a purchase, a booked call. In GA4 you mark those as key events so reports highlight them. (Older guides call these "conversions".)
Engagement, not bounce
GA4 counts a session as engaged if the visitor stayed a meaningful time, viewed more than one page, or triggered a key event. Engagement rate is the share of sessions that were engaged — a more useful number than old-style bounce rate.
💡 Real-world example
An online course site wondered why its traffic reports looked healthy but sign-ups were flat. Once they understood that a sign-up was just another event — and marked sign_up as a key event — they could see which traffic sources produced sign-ups, not just visits.
✅ Checklist
🛠 Your assignment
List the 2–4 actions on your website that show real business results (for example sign-up, lead form, purchase, call click). These will become your key events.
📝 Check your understanding
Answer 2 of 3 correctly to complete this lesson.