Here is some basic information for people who want help identifying popular styles of dance music.
HOUSE is thought to have started in the Warehouse Club in Chicago in the 80's, the resident DJ Frankie Knuckles mixed together Disco and electronic music. House has a classic solid four beats to the bar at a tempo of 120 - 130bpm, it usually has a kick drum on all four beats with a snare and/or hand clap on beats two and four, hi hats are on the off beats, there can be a few vocals, a piano loop and simple bass lines.
GARAGE was named after the Paradise Garage in New York and started in the mid 80's, Garage is similar to House but evolved from Soul music, there's more use of melody and vocals, the tempo is between 120 - 130bpm.
ACID is synthesized drums using machines like the Roland TR-909 and squelchy bass lines using the Roland TB-303, vocals are minimal and the tempo is up around 140 - 150bpm.
TECHNO covers a vast range of styles from Electro Pop of the 70's to the distorted sampled sounds of Hardcore, its main characteristics are the four-to-the-floor beat, heavy sounds, repetition and electronic content, its usually at 125 - 145bpm, it can have vocals though they are few and usualy sampled. Techno was developed in Detroit in the 80's with the mass parties known as raves.
IDM (Intelligent Dance Music) is Techno to be listened to not danced to, its more musical and ambient, usually at sub-100bpm.
TRANCE is best described as danceable Ambient, normally played at around 140bpm with a four-to-the-floor beat, repeating arpeggiators, synth effects and layered sounds.
DRUM & BASS is usually created with a sampler and uses chopped up breakbeat rhythms often syncopated, the tempo is around 140 - 160bpm the fast rhythms are played against slow bass lines influenced by various other genres as well as Reggae.
HIP HOP generally has a slow, lazy feel at around 90bpm, often with soul and funk influences and has rhyming rap lyrics over the rhythm.