UTM parameters
UTM parameters (Urchin Tracking Module) are tags appended to campaign URLs to identify in analytics the source, medium, campaign name, term, and content of an incoming click. Without them, many visits are misattributed to Direct or Referral in reports.
In practice
The five standard parameters: utm_source (google, newsletter), utm_medium (cpc, email, social), utm_campaign (campaign name), utm_term (keyword for paid search), utm_content (differentiate two variants). Without UTMs, GA4 attributes email visits to 'Direct' and social visits often to 'Referral'. A documented UTM naming plan shared across the team prevents duplicates and reporting inconsistencies.