Brett is Nora's boyfriend (later ex-boyfriend) in the movie.
Step Up Edit
When the movie started, Brett was Nora's boyfriend. After acquiring a recording deal he decided that his friends weren’t important anymore and began to flirt with other girls. He didn't bother to talk to Nora about it and she had to find out from someone else. She dumped him because of his behavior.
Brett is egotistical and generally only thinks of himself. Nora described him as "stepping on his friends" to get to the top. At first he does seem like the type who might care about Nora because he seems concerned when she starts to hang out another guy but the audience is proved wrong.