UTM parameters are used in most analytics platforms. Popularized by Google Analytics, they act as information gatherers for identifying what sent a user to your site. For example, you might include a link in an email campaign and want to know exactly which visitors arrived from it in your analytics data, so you might add ?utm_medium=email to the end of the URL.

UTM is an acronym for Urchin Tracking Module, still named after the company that Google bought and released as Google Analytics in 2005.