Can you transfer apps from downloads to itunes library?

Is there a way to download iphone apps to the computer and then transfer them to itunes? I tried this with minecraft PE and it popped up in itunes and started to install but it came up on my ipod touch "can't install".Is there something I did wrong or is it just not possible?

IPhone apps have copy protection, so if you don't get them the official way, you'll have trouble. You actually can transfer apps you got through iTunes, but they include your account information so only you can use them.