I read about working the "buns". But how important is working the "buns" for bodybuilders? I mean, I understand all areas need work, but any specialization here?

When it comes to bodybuilding and general exercise, the buns (aka gluteus maximus) are just as important as any muscle. There are a multitude of exercises that involve the glutes such as squats, deadlifts, lunges, running, bench pressing, I would say almost all exercises involve the glute area in some shape or fashion.