A conversion is an action that is counted when someone interacts with your ad. For example, someone 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 types of tracking to measure conversions depending on the action someone takes when interacting with your ad. Conversions can be tracked across different devices like mobile and desktop.