UTM Parameters
Intermediate PronunciationEN/ˌjuː tiː ˈɛm pəˈræmɪtərz/
UTM parameters are tags appended to a link so each visit can be traced to its campaign, channel and source.
There are five standard parameters: source, medium, campaign, plus term and content when needed. Without UTMs, campaign traffic blends together in reports and you cannot tell which ad spend paid off.
Sources:Wikipedia — UTM parameters