App install ads allow users to install apps directly by clicking on the ad. Based on where the ad appears, any original content may be added to, removed, or modified during the ad serving process. Facebook does this to help make sure that users get a great experience from the ad no matter when and where they see it.   Mobile apps are a huge part of marketing today. In a world where competition for both clients and online attention is high, mobile apps can help keep users thinking about and engage with brands they see.