In Google Analytics, one segmentation that assists site owners, marketers and overall decision makers determine their effectiveness is the Traffic Source. Though we can view crucial information pertaining to how our site visitors were acquired, there may be none more informative that Traffic Sources. Analyzing sessions, new users, bounce rate ecommerce conversion rates, transactions, goals and more is pointless unless you can determine WHERE the traffic was from. The traffic source dimensions are:
Source: This is simply the origin or the name of a referring site. Examples are Google, facebook.com, Direct, or Bing
Medium: This tells you the type of site the referring site is. Basic traffic mediums include organic, cpc, referral, email and none. None, in this case, is usually attached to the Direct source type, as opposed to not having a medium.
Keyword: Unless designated with a UTM tracking parameter, keyword will return the value of not provided.
Campaign: Either refers to the name of the Google Adwords campaign or if you are using UTM campaign names for custom advertising campaign tracking.
Content: Most often used to differentiate different link or content values in custom campaigns.
See our post on UTM tracking, for further explanations.