Well, you could consider them 'low - lifes'. In the world of 'Pulp Fiction', the characters are often morally ambiguous. They do all sorts of seedy things. So 'low - lifes' kind of sums up their general nature. They are not exactly model citizens, and they live on the fringes of society, getting involved in all kinds of underworld affairs.
You could call them 'rogues'. In 'Pulp Fiction', the characters have a certain charm despite their immoral actions. They are not your typical good guys. They are more like rogues who live by their own rules and are not afraid to take risks and do things that most people wouldn't dare to do. They are unpredictable and often cause chaos, which is characteristic of rogues.
Well, for one, it's a break from the intense moments in the movie. The light-heartedness and the fun of the dance add a nice contrast. Also, the performances of the actors and the choreography are top-notch.
The two types could be the talkers and the doers. In Pulp Fiction, some characters like Marsellus Wallace are more about getting things done, being in control and making things happen. Then there are characters like Vincent Vega who are more talkative, always chatting about different things, whether it's about foot massages or the differences between Europe and America. They represent different aspects of the film's complex character set.
I'm not sure which specific 'Pitt' you are referring to in 'Pulp Fiction'. There isn't a major character named Pitt in the movie as far as I know. Maybe it's a name you associated with it in a different context.