Y tu vs Y usted
The difference between Y tu and Y Usted is that one is formal while the other is informal. Y tu is informal and Y Usted id formal. In Spanish we change the way we speak when talking to someone we have respect for and are an adult rather than our friends. When talking to an adult we use formal language when talking to our friends we use informal language. They both still mean the same thing.
Real life application
A student is talking to a student and than an adult.