The U.S.-Iraq Status of Forces Agreement is a legal agreement between the United States of America and Iraq that talks about what American military service members are allowed to do while they are in Iraq.
You know how when you're playing with your toys at a friend's house, you have to follow their rules? It's kind of like that. When American soldiers are in Iraq, they have to follow the rules that Iraq says are okay.
The agreement is like a big list that tells the American soldiers what they can and cannot do in Iraq. It also says how long they can stay in Iraq and how many soldiers are allowed to be there.
Both sides have to agree to the rules, which is like when your friend and you agree to play a game together. It's important to have these kinds of agreements so that nobody gets hurt, and everyone knows what they can and cannot do.