A pub is considered to be a place wherein people can drink booze whenever they want to. This is known to be a place wherein people can hang out, and they can expect both alcoholic and non-alcoholic drinks to be served. A club can be considered to be a place wherein people will not usually be on tables but will be on the dance floor.
They would all be dancing on the dance floor with their partners, with their friends, and even new people that they will meet there. It will be harder to have discussions inside the club because the music is usually turned up higher, and people are usually more intoxicated.