Pass information between applications (Android/iOS)

Hi, i develop an Unity game who needs to be integrated in an existing Android / iOS app, and for now all works perfectly for both the platforms... my question is: how can i pass some information when i open Unity with Android and iOS? I have to know for what type of game Unity is opened, only that.
I imagine there are a lot of ways to manage this think, but maybe the best is to pass some infos when i open the app in the start method, but i don't know how to do that.
Any suggest?