Dips, or any exercise, can work any muscle but it depends on how you do them. I love dips so let me explain....
If you do dips, generally, they will work pec major, anterior deltoid ( front muscle of three shoulder muscles) and triceps.
If you keep your body upright and your elbows back, it is mostly triceps and pec major.
If you lean forward and flare your elbows out, it will activate more pec major, but tris and shoulders still work.
If you lean forward, same as before, but at the top push a bit more so that your shoulders come together, it will activate the pec minor. Pec minor only pulls the shoulders forward and together. BUT, if worked it pushes the pec major up and out and makes them look deeper and thicker.
Anyone that is serious about working out should buy a cheap anatomy book so that they can see what is what and what attaches to what. For the cost of two Muscle and Fitness or Men's Fitness mags you can have a book that will answer most questions and is well worth the price.