Source: Every referral to a web site has an origin, or source. Possible sources include: “google” (the name of a search engine), “facebook.com” (the name of a referring site), “spring_newsletter” (the name of one of your newsletters), and “direct” (users that typed your URL directly into their browser, or who had bookmarked your site).

Medium: Every referral to a website also has a medium. Possible medium include: “organic” (unpaid search), “CPC” (cost per click, i.e. paid search), “referral” (referral), “email” (the name of a custom medium you have created), “none” (direct traffic has a medium of “none”).

Keyword: When SSL search is employed, the Keyword will have the value (not provided).

The campaign is the name of the referring Google Ads campaign or a custom campaign that you have created.

Content identifies a specific link or content item in a custom campaign. For example, if you have two call-to-action links within the same email message, you can use different Content values to differentiate them so that you can tell which version is most effective.