Sasha, DJ Sneak and The Chemical Brothers or SHM, Skrillex and Calvin Harris - "mainstream" or "underground" - it doesn't matter. It's electronic music.
We obviously all have our own tastes and niches which we swear by and these subgenres & micro-scenes will always shape the way we express ourselves and perceive other sounds, however... Electronic Dance Music, or "EDM", is music that is produced electronically, that makes you dance.
It's simple and it doesn't need to be any more complicated than that.
Listen to what you want, call it what you want - but just please be respectful of others and avoid pigeonholing an acronym that at its root is meant to be inclusive.
