What is the squealing noise coming from my car?

What is the squealing noise coming from my car?

Added (1). My car is a 2006 Honda Civic. It makes a loud squealing from what sounds like the front driver's side. It stops when I brake and usually starts when I accelerate. It also does it when I just start my drive to work but usually is gone by the time I get there. It squeals at least once per drive, sometimes the entire trip, sometimes just for a moment. My boyfriend said that it doesn't sound like a belt problem, but he isn't sure.

Any ideas?

Slipping serpentine belt. Needs either tightening or replacing if damaged.

Breaks?