EDM stands for ‘Electronic Dance Music' and is an umbrella terms for all of the different electronic music and dance music sub-genres. IDM on the other hand stands for Intelligent Dance Music and is focused heavily on experimentation. So in a way, IDM falls under the EDM umbrella for all things dance music.
Some of today's most popular IDM artists are Aphex Twin, Squarepusher, and Baseck.
