What is the difference between them all? I saw online that on my mac desktop, the itunes is an app that contains iOS apps to buy, and the app store on my mac desktop is for buying desktop apps for my computer. I understood this. but what about on my devices such as my iphone and ipad? I notice they both have itunes and an app store. Is the itunes my devices just for buying music? is the app store on my devices just for buying accessing my iOS apps?