Attribution
As an advertiser, you need to understand which of your ads contributed to a conversion. How you determine which part of your advertising should be attributed to the value of the conversion is called attribution.
Let us explain this with an example:
A customer performs a conversion on your site, e.g. buys a product or fills out a contact form after clicking on an ad. We could then credit that ad with the full value of the conversion, but is that really true? The ad was probably not the only contact the customer had with your company before deciding. What about the banner ad he clicked on last week? The YouTube video he saw the day before he clicked on the ad? Shouldn’t they get some of the credit?
By analyzing the attribution, you can quantify how each channel contributes to sales and conversions.
The various advertising platforms and analytics tools use different, standardized attribution models to credit value. Here you can read more about these.
In the Google Analytics Support Center, Google has explained attribution as follows.