A medium is a category of traffic sources used to identify the type of referral that brought a user to a website. The medium categorizes the referral source into one of the following categories:
- Organic: The user arrives at the website via a search engine, such as Google or Bing.
- CPC: The user arrives by clicking on an advertisement.
- Referral: The user arrives by clicking on a link on another website or web application.
- (none): The user arrives by typing the URL directly into their browser or using a bookmark.
- Email: The user arrives by clicking on a link in an email.
The medium can be used to optimize marketing and advertising campaigns.