Attribution is used to comprehend the holistic journey someone takes when they interact with your marketing campaigns. This information will help you understand what contributed to someone interacting with one of your programs.
In order to run a successful marketing campaign, you need to understand all of the influences that drive conversions through the funnel, and attribution helps you identify what parts of the conversion path are the reason targets engage.
To access the Attribution Overview, navigate to Attribution > Overview.

This is what the Attribution Overview dashboard looks like:

From here you can see a quick overview of your marketing campaigns, marketers, promotion tracking, and attribution trackers.
Each section of the Attribution Overview has its own documentation explaining the different aspects of that attribution component.