An organic install is an app download coming from a search on an app store, a browse on the top charts or app categories, friend reference, or word of mouth. In order for an install to be considered as organic, it should not be attributed to any mobile ad campaign. However it doesn’t mean that the user is not exposed to a mobile ad. An organic user can see an ad but he doesn’t interact with the ad and then he prefers downloading the app by searching it from an app store. 

For mobile app developers and app-based companies, it is not easy to gain organic installs because of the harsh competition in almost all app categories and countries. This is why they prefer executing App Store Optimization to let users find their apps organically.