From Hits to Events: A Comprehensive Glossary for Mastering Google Analytics 4

Douglas KarrMay 14, 2021

5 minutes read

From its early beginnings tracking simple hits and pageviews in Urchin and Universal Analytics, Google’s measurement platform has undergone a radical transformation. The original model—based on sessions and categories of hits like pageviews, events, and ecommerce—was built for a desktop-centric web. But today’s digital landscape spans mobile apps, cross-device behavior, privacy regulations, and increasingly complex customer journeys.

Google Analytics 4 (GA4) is not just an upgrade—it’s a complete rethinking of how user behavior is measured. Instead of treating events as one of several hit types, GA4 makes every interaction an event by default. It decouples data collection from rigid hierarchies, enabling marketers and analysts to define their events, parameters, and audiences. Machine learning (ML), predictive modeling, and enhanced privacy controls are now core features. And with cross-platform tracking built in, GA4 offers a more holistic and future-proof foundation for understanding user engagement.

This glossary organizes the core vocabulary used in Google Analytics 4 (GA4), grouped into intuitive categories and listed in alphabetical order within each category. It includes user-facing and backend concepts across all areas of the platform, including the Admin panel, standard and custom reports, DebugView, Realtime, and advanced configuration settings. GA4-specific definitions are provided where the platform differs from Universal Analytics.

Accounts and Properties

Account: The highest level of organization in GA4, representing the container that holds one or more properties.
Property: A GA4 entity where data from one or more data streams is collected and reported.
Measurement ID: The unique ID assigned to each GA4 data stream (e.g., G-XXXXXXX), used to route data.
Admin Panel: The area for managing account and property settings, including integrations, users, and data configurations.

Data Collection and Structure

Data Stream: A source of data flowing into a GA4 property, such as a website or mobile app.
Event: The core data unit in GA4, representing any user interaction or system occurrence.
Event Parameter: Metadata attached to events to provide additional context (e.g., page title, video duration).
Custom Dimension: A user-defined text attribute added to events or users for custom reporting.
Custom Metric: A user-defined numeric attribute attached to events.
Custom Definitions: The umbrella term for custom dimensions and custom metrics.
User Property: Persistent attributes about a user, like subscription level or preferred language.
User-Provided Data: Hashed or pseudonymized user data (e.g., email address) collected for advertising and attribution.
PII (Personally Identifiable Information): Forbidden in GA4—personal data like names or emails must not be sent.

Traffic and Campaign Attribution

Acquisition: Describes how users arrived at your site or app.
Source: The origin of traffic (e.g., google, newsletter.example.com).
Medium: The general category of the traffic (e.g., organic, referral, cpc).
Campaign Name: The label used to identify a specific campaign (typically derived from utm_campaign).
Campaign Tags: UTM parameters added to URLs to track traffic origins.
UTM Tag: URL parameters (utm_source, utm_medium, etc.) used for campaign tracking.
Referral: Traffic coming from other websites (non-search engines).
Organic: Non-paid traffic from search engines or social channels.
Direct: Traffic where no referrer or campaign data could be determined.
Google Ads: Google’s ad platform, tightly integrated with GA4 for campaign tracking and attribution.
Enhanced Conversions: Uses hashed user data to improve ad conversion tracking.
Lookback Window: The time window before conversion during which touchpoints are considered for attribution.
Attribution: The method by which GA4 assigns credit for conversions across touchpoints.
Google Signals: Enables cross-device tracking and richer audience data using signed-in Google user data.
First User Medium: The medium of a user’s first session.
First User Source: The source of a user’s first session.

Audiences and Segments

Audience: A group of users defined by shared characteristics or behavior, used for filtering or remarketing.
Segment: A subset of data (users, sessions, events) used for in-depth analysis, especially in Explorations.
Predictive Metrics: Machine learning–based metrics that predict user behavior (e.g., purchase probability).

Sessions and Engagement

Session: A period of user interaction on your site/app; begins with a session_start event.
Session ID: A unique identifier for each session.
Session Start: The event signaling the beginning of a session.
Engaged Sessions: Sessions that last 10+ seconds, include a conversion, or have multiple views.
Engagement Rate: Percentage of sessions that qualify as engaged.
Bounce Rate: The inverse of engagement rate; sessions with no meaningful engagement.
Average Engagement Time: The average time users actively spent engaging with content.
Average Engagement Time per Session: Average engaged time per session.
User Engagement: Time users are actively interacting with the site or app.
Sessions per User: Average number of sessions per user.
Engaged Sessions per User: Average number of engaged sessions per user.
Events per Session: Average number of events triggered per session.
Views: Total number of page views or screen views.
Views per User: Average number of views per user.

Ecommerce and Monetization

Conversion: An event marked as important to the business (e.g., purchase, sign-up).
Key Event: Another term for a designated conversion event.
Ecommerce Purchase: A purchase event including transaction details.
Monetization Reports: GA4’s reports tracking revenue, purchases, and ad monetization.
Lifetime Value (LTV): The total value a user contributes over time.

Reporting and Analysis

Reports: Standard GA4 dashboards covering user behavior, acquisition, and more.
Exploration (Explore): Custom report builder for advanced data analysis.
Funnel Exploration: A custom report visualizing steps in a process (e.g., checkout flow).
Cohort Exploration: Tracks behavior over time among users who started during the same time period.
Cohorts: Groups of users defined by their start period.
Explorations Snapshots: Saved views of Exploration results.
Comparison: Side-by-side filtering option within standard reports.
Library: Interface for customizing and organizing GA4 reports.
Realtime Report: Displays live user activity from the past 30 minutes.
Traffic Acquisition Report: Shows sessions by source/medium/channel.
User Acquisition Report: Shows first-time user acquisition sources.
Landing Page: The first page a user views during a session.
Search Query: The term a user searched for (external or internal search).
(not provided): Placeholder for unavailable search query data.
(not set): Placeholder for missing dimension or parameter data.

Technical Configuration

Google Tag (gtag.js): The tracking code used to collect GA4 data.
Google Tag Manager (GTM): A tag management system for deploying analytics and marketing tags.
Connected Site Tags: Allows multiple GA4 properties to share a single site tag.
Consent Mode: Adjusts tracking behavior based on user consent status.
Consent Signals: Indicators sent to GA4 about a user’s consent choices.
Enhanced Measurement: Auto-collection of common user interactions (e.g., scrolls, downloads).
Behavioral Modeling: Uses machine learning to estimate behavior from users who decline cookies.
Data Filter: Tool to include or exclude traffic (e.g., internal or test traffic).
Data Import: Lets you upload external data (e.g., costs, CRM info) into GA4.
Data Retention: Duration for which detailed event/user data is stored.
Change History: A log of all administrative and configuration changes.
Annotations: Notes added to reports for context (e.g., site launch, campaign start).
Client ID: A randomly assigned ID for each browser/device.
Device ID: Unique identifier for the user’s device (browser or app instance).
User ID: An identifier you assign to a known user, allowing cross-device tracking.
Default Channel Group: Predefined buckets of traffic sources (e.g., Organic Search, Referral).
Default Reporting Identity: Determines how GA4 merges user activity across sessions/devices.
Threshold: Privacy mechanism that withholds or aggregates data for low-volume user groups.
Sampling: When GA4 uses a subset of data to estimate values, typically in Explorations.
Regex (Regular Expression): Pattern syntax for flexible filtering and matching.
Measurement Protocol: API allowing server-side or offline data to be sent into GA4.

External Tools and Integration

BigQuery Export: Sends raw GA4 data to Google’s BigQuery for advanced querying.
Looker Studio: Google’s dashboard and reporting platform (formerly Data Studio).
URL Builder: Tool for generating UTM campaign-tagged URLs.
Benchmarking: Optional feature for comparing your metrics to industry aggregates.

As analytics evolves from hit counters to event-based models, the ability to understand and apply this vocabulary becomes essential for marketers, analysts, and developers alike. GA4 may feel like a significant shift—but with this glossary as your guide, you’re equipped to speak the language of modern digital measurement and unlock the platform’s full potential.