Definition:
"Doors" is a slang for the time that a venue opens up to allow concert goers in for a music show. It is short for "doors open." Doors are usually an hour or so before the music is slated to start, so the audience can get in, get settled, and of course, spend some money at the bar!
If you're planning a gig, you might be asked, "what time are doors?" and that means, "what time can the audience start coming in to the venue?"
