With conversion tracking, you can see which of your ads led to your website conversions. In your ads reporting, this is broken up into 1-day, 7-day and 28-day attribution windows. We also break up this info by click-through conversions (a customer clicked your ad and converted) and view-through conversions (a customer saw your ad, didn't click it, but converted).
Things to keep in mind:
If a customer clicked an ad, a conversion can only be attributed to the click. If that customer never clicked an ad, but still converted, a conversion can only be attributed to the view. Conversions cannot be simultaneously attributed to both.
Clicks take precedence over views, even if the view happens after the click.
Conversions are attributed to the most recent ad someone clicked. If they didn't click, it's attributed to the most recent ad they saw.
Any events outside the maximum conversion window (28 days) are not considered.
Here's an example to help explain:
On Monday a customer viewed your ad and clicked it but didn't make a conversion. Later, on the following Tuesday (8 days later) that same customer viewed the ad again, didn't click, but converted. If you opened up your reports after the conversion happened on Tuesday, this is what you'd see: