Hey people. I have a question regarding the architecture of mobile apps like fore iPhone and android. I have written an application in objective c for iPhone but I need to know how the 3 layers/tiers are: Tell me if i am doing this right: The presentation layer/ front end : the GUI made in interface builder. And / or for android. Business logic : I don't know what that is in my application Back end / database server layer: I have a back end in parse but my code is in Xcode not on any server. So is this a good explanation for an essay ?