(Marketing) attribution is the process of identifying and crediting the various marketing activities and touch points that contribute to a desired outcome, such as a sale or conversion. It helps advertisers understand the effectiveness of each marketing channel, campaign, or tactic in driving customer actions and revenue.

Common attribution models include:

1. First-Touch Attribution: Credits the first ad impression or click
2. Last-Touch Attribution: Credits the last ad engagement (impression or click) before conversion

While attribution is an important method, attribution tends to over or under attribute certain mediums and ad platforms, relying on the nature of tracking impressions, clicks, and users. 
Advertisers typically will use attribution in combination with other methodologies of measurement.