What is Source vs. Referrer vs. UTM Source vs. UTM Medium?

Source

By default "Source" is the "?utm_source=" (From our Website Script) parameter in URLs that people visit. If "?utm_source=" doesn't exist, "Source" is pulled from the referrer.

Referrer

"Referrer" is pulled from the referrer URL (the webpage a person was on right before they landed on your page).

UTM Source

"UTM Source" is the "?utm_source=" in URLs that people visit. For example, if someone visits hockeystack.com/?utm_source=google, UTM Source is google.

UTM Medium

"UTM Medium" is the "?utm_medium=" in URLs that people visit. For example, if someone visits hockeystack.com/?utm_medium=cpc, UTM Medium is cpc.