Are cows mean? Do they bite or attack you?

I think they're so cute, but they look really mean! I mean, people go near horses all the time and they seem like nice animals... but you don't see people around cows that much. I was just watching videos on youtube and saw a lot of people around the colt/foal when they were first born and helping them stand, and the mother not minding it. But of all the videos of the calves, the people kept their distance. Are cows more protective of their young or just more aggressive?