A postback is an attribution type where attribution providers notify mobile ad networks in the meantime an app install or in-app event happens. It is important for app developers and mobile advertisers to understand the campaign data and optimize the campaigns accordingly. 

Both install postbacks and in-app event postbacks should have some important data including Device ID, app ID, location, and much more. Advertisers can decide on which data they want the attribution provider to send to the mobile ad network.