An action that's counted when someone interacts with your ad or free product listing (for example, clicks a text ad or views a video ad) and then takes an action that you’ve defined as valuable to your business, such as an online purchase or a call to your business from a mobile phone.
Conversions are measured with conversion tracking. You can use different tracking processes to measure conversions depending on the action someone takes when they interact with your ad or free listing. Conversions can be tracked across different surfaces (such as mobile or desktop) and may include modeled conversions. Modeled conversions use data that does not identify individual users to estimate conversions that Google is unable to observe directly. This can offer a more complete report of your conversions.