"Sessions are the number of visitors, right?" "Page views are high, so traffic is healthy." These are the most common mix-ups I hear from people starting out with web analytics. Sessions, page views, and unique users (UU) look similar but mean different things, are counted differently, and are used for different decisions. This article walks through what each of the three metrics actually counts, how they relate, which one to look at first, and how GA4 treats them under its event-based measurement model. The three metrics count different things: Sessions = visits, PV = pages viewed, Users = people who visited. One person visiting 3 times and viewing 5 pages produces Sessions=3 / PV=5 / Users=1 Base inequality is PV ≧ Sessions ≧ Users: a person typically makes multiple visits and views multiple pages per visit, so PV is largest and Users is smallest EC priority: Users first, then repeat rate, then engagement: start with Users (reach), then Sessions/Users (repeat rate), then PV/Sessions (engagement depth) A session is the time period during which a user interacts with a site, counted from arrival to leaving as a single unit. A session ends automatically after 30 minutes of inactivity, and a new day (midnight) starts a new session. If someone visits at 9 AM, views 3 pages, leaves, and comes back at 8 PM the same day, that counts as 2 sessions. Even within the same day, a gap longer than 30 minutes creates a new session. Common confusion: "Sessions = visitor count" is wrong. The same person visiting 5 times a day produces 5 sessions, not 1. In GA4, every session start fires a session_start event, incrementing the session count by 1. A session_id groups all actions (page views, clicks, purchases) inside that window. A page view is one count for every time a page is loaded. Opening the same page twice creates 2 page views. Reloads count. A flow of "Home → Product A → Home → Product B → Cart" produces PV = 5 because Home was visited twice. Common confusion: "High PV = popular site" is wrong. A small group of users clicking around can inflate PV. Always read it alongside PV / Sessions (engagement depth). In GA4, PV is recorded as the count of page_view events. Reports may show it as "Views" or "Page views", but internally it is just the count of page_view events. UU is the number of distinct people who visited in a given period, identified via Cookie or User ID. The same person visiting 10 times still counts as 1 user. Visiting from another browser or device produces a separate user. Monthly UU = 1,000 with 200 repeat visitors averaging 3 visits each means new-user sessions = 800, repeat-user sessions = 200 × 3 = 600, so total monthly sessions = 1,400. Common confusion: "UU = exact number of real people" is wrong. Cookie deletion and multi-device use inflate the number; users who reject Cookie consent are excluded. In GA4, this appears as "Active Users". A user is marked active when an engagement session occurs (a session GA4 considers meaningful) or when a first_visit event fires. The base inequality is: PV ≧ Sessions ≧ Users A person typically makes multiple visits, and each visit views multiple pages, so PV is largest and Users is smallest. Equality only holds in an extreme case where every user makes one single-page visit. Derived combinations are what matter in practice. PV / Sessions = pages per visit (engagement depth). Sessions / Users = visits per user (repeat rate). PV / Users = pages per user (interest depth). For EC operators, the priority order is Users → Sessions/Users → PV/Sessions: how many people are coming, then how often they come back, then how much they explore. Reading PV alone is dangerous. A small number of users clicking around can produce inflated PV while new-user inflow is actually zero. Health becomes visible only when reach, repeat rate, and engagement depth are read together. GA4 switched its measurement model to event-based. This is a fundamental shift from Universal Analytics (UA), which was session-based. Every action — page view, click, scroll, purchase — is recorded as an event. Sessions, page views, and users are computed as aggregations of those events under the hood. Sessions = count of session_start event fires. Page views = count of page_view event fires. Users = displayed as "Active Users", aggregated from engagement signals. The words "sessions" and "page views" still exist in GA4 reports, but internally they are derived from event counts. Understanding this model makes debugging unexpected GA4 numbers much faster. Three metrics, three different things being counted. The base inequality PV ≧ Sessions ≧ Users is the anchor. Read combinations (repeat rate, engagement depth), not single metrics. Start with Users — the rest of analytics flows from there. If you found this helpful, the full version with references and related articles is at the canonical URL above. What metric do you wish someone had explained to you earlier in your analytics journey?