What are the differences between club dances and modeern standard dances?

Well, ballroom dancing is actually divided between three categories: rhythm/latin, smooth/standard, and club.

Rhythm (american style) and latin (international style) dances are danced in one spot and for the most part have cuban/south american influences in the music and hip motion: rumba, cha cha, samba, bolero, paso doble, mambo. For the purposes of competition, EC swing and jive are usually lumped in with this.

Smooth (american style) and standard (international) travel around the floor. They do not have hip motion: waltz, foxtrot, tango, quickstep, viennese waltz.

Club dances include salsa, merengue, night club two step, swing. These are the dances that you might do in a 'club' setting...the technique is a little more relaxed than the other dances.

Does that help?