Source is one of the four main dimensions (along with Medium is one of the four main dimensions (along with source, campaign and channel) for re, The top-level structure of your account, think of campaigns as folders within your account and Channels provide top-level groupings of your inbound marketing. Each channel combines sour) for reporting and analyzing how people found your website. Source tells you where the message was seen. For example, a source of ‘google’ would indicate that someone found your website after performing a search on Google. Source can be used in combination with medium for more granular insights, for example, a source of ‘google’ and a medium of ‘cpc’ would be reported for paid clicks from your AdWords campaigns.