How GA4 Works for Marketers: Events, Users and Sessions
GA4 explained for marketers: everything is an event, how users and sessions are counted, and what that changes in your reports.
GA4 counts every interaction as an event, then builds users, sessions and channels on top of those events. Once you think in events (page_view, generate_lead, purchase), the rest of GA4 makes sense: key events are events you flag as important, reports group events by dimensions, and explorations let you slice them freely.
- The data model is events with parameters. Page views, scrolls, clicks and purchases are all events.
- A property holds your reports; a data stream (web or app) feeds it.
- Sessions start with a session_start event; channel and source are attached per session and per first visit.
- Key events replaced "conversions" in GA4's naming. Lesson 4 covers them.
- Standard reports are aggregated; explorations are more flexible but limited by your data retention setting.
Checked 4 November 2026 (CET) against Google Analytics Help and Google developer documentation. GA4 menus and limits change, so confirm in your own property. "Our view" marks MentionX opinion. Ledgerline is a fictional company used for illustration.
01What does "everything is an event" mean in practice?
Each hit GA4 receives has an event name and a set of parameters. A page view is page_view with parameters such as page_location and page_referrer. A form submission you track might be generate_lead with a form_id parameter. Reports count these events and group them by dimensions such as page, source or country.
| Concept | What it is | Marketer's question it answers |
|---|---|---|
| Event | One interaction with a name and parameters | What did people do? |
| Parameter | Detail attached to an event | Which form, which video, which value? |
| User | A browser or app instance, joined with other IDs where available | How many people? |
| Session | A group of events from one visit | How many visits, and from where? |
| Key event | An event you flag as important | Which visits produced results? |
| Dimension / metric | A label (source) or a number (sessions) | How do I cut the data? |
02How are users and sessions counted?
GA4 gives each browser a pseudonymous ID through a first-party cookie. If you send a user ID for logged-in users, or if Google signals is on, GA4 can join activity across devices. Because of consent choices, ad blockers and cookie limits, user counts are always an estimate, not a headcount. Lesson 13 covers how consent mode affects what is collected.
03Where does traffic source come from?
GA4 reads UTM parameters, Google Ads click IDs and the page referrer when a session starts, then assigns a channel using the default channel group rules. Lessons 5-7 cover tagging, the default channels and the AI Assistant channel.
04Reports or explorations?
Use Reports for recurring numbers that the whole team reads. Use Explore for one-off questions, funnels and paths. Explorations depend on your data retention setting, which is 2 months by default on many properties, so lesson 2 tells you to change it on day one.
Our view: marketers get more from GA4 by tracking five meaningful events well than by tracking fifty loosely. Start with the actions that map to pipeline or revenue.
05Example: Ledgerline's first look
Ledgerline, a fictional accounting software company, opened its property and found page_view, scroll, click, form_start and form_submit from enhanced measurement, but nothing for demo requests. Its first task was a generate_lead event on the demo form, flagged as a key event (lesson 4).
Next: GA4 property setup checklist for marketers. Or return to the GA4 for Marketers track.
06Common questions
Is GA4 session-based like Universal Analytics? No. GA4 records everything as events. Sessions still exist, but they are derived from a session_start event and a session ID rather than being the core unit.
What is the difference between a property and a data stream? A property is where reports live. A data stream is a source feeding it, such as one website or one app. Most marketing sites need one property with one web stream.
Do I need Google Tag Manager to use GA4? No. The Google tag (gtag.js) is enough to start. Tag Manager helps when you add many custom events or need consent controls without code changes.
Questions people ask
3 answersIs GA4 session-based like Universal Analytics?
+
No. GA4 records everything as events. Sessions still exist, but they are derived from a session_start event and a session ID rather than being the core unit.
What is the difference between a property and a data stream?
+
A property is where reports live. A data stream is a source feeding it, such as one website or one app. Most marketing sites need one property with one web stream.
Do I need Google Tag Manager to use GA4?
+
No. The Google tag (gtag.js) is enough to start. Tag Manager helps when you add many custom events or need consent controls without code changes.
Sources
- Google Analytics Help, About eventssupport.google.com
- Google Analytics Help, Set up Analytics for a website and/or appsupport.google.com
- Google Analytics Help, Enhanced measurement eventssupport.google.com
- Google Analytics Help, Data retentionsupport.google.com
- All accessed 4 Nov 2026.