How are reminders done???

I have a few games installed on my iPad mini, that once in a while they'll be a sort of a pop up or reminder saying whatever when the game is not even running. Cover Orange, Temple Run and so forth do this. How is that done? Is it a small app that always runs in the background and if you don't play the game for a long period of time, it triggers the ad?

For iOS native apps these reminders are called Push Notifications: https://developer.apple.com/notifications/

Ahh,.thanks bud!! Pretty cool. Can this be done with Android apps?

I'm currently not developing for Android, but a quick search returned Google Messaging for Android:
http://developer.android.com/google/gcm/index.html

Hi Olivier. Can push notifications be set up using Clickteam Fusion. So if say, i made a new game, i could let send out a notification on my old game to tell them to try my newly released game? :)

That's a good idea. But I don't know how push notifications must be implemented, as I've never used them. You should check the links I posted above for further information. And maybe someone with the knowledge could give a better answer.