On iTouch, how do the Apps work?

I plan on getting the 32GB iTouch next month, and I was looking through some of the Apps on the Apple Store, but I saw that some said some stuff like "Experience the iPhone with this app" and "finaly u can send pictures to different "iPhones" even though I went to the iTouch Apps. How do I know which ones work for the iTouch?? If u have it, is it worth it?? [i have a 30gb regular iPod, but I want games lol] I save alot of photos and video to the iPod as like a stoarage device [where u open the ipod in the "computer" section.] and how to go I GET the APPS?? Like if I DONT have wifi? and when I DO have a wifo spot, how do i get the FREE apps??