So I know someone who got the S3 recently and it's almost my first real experience with a smartphone. I've understood everything and know how to teach it back, but one thing I don't understand about multitasking in general is what does pushing the middle button do? Does it hide or close the current screen/application?
Also, data usage can be an issue. It says the OS has used 88MB in background processes. What does that mean and does that blow through the data cap?
The middle button is your home button. When you press it it'll take you back to your homescreen. Pressing and holding it will take you to a list of the previous apps you have used and you can switch to that app by pressing on the picture of it.
When the OS says it uses 88MB in background processes, that is RAM. It is not your mobile data. If you're worried about blowing through your data cap, you can go into settings, then data usage, then check the box that says set mobile data limit and adjust the graph to where you want it to warn you or disable mobile data and such.