SpiderBasic - InAppPurchase
In-App purchase is a system supported by GooglePlay and iOS AppStore to buy items directly from inside an application. It is mostly used for games, but can used for any kind of application to unlock special features against a fee.
For Android, the GooglePlay public app API key needs to be specified in the create app dialog. It can be found in the google play console 'Service & API' -> 'Public key RSA for this app' (the key which looks like: MIIB......AQAB).