Music magazine that focuses on new metal bands, some rappers, alternative rock, and related bands. AP has been in publication since December, 1987 and isn't as Top 40 oriented as other music magazines like Rolling Stone, Spin, etc. This isn't to say the artists AP covers aren't popular, they're just not people like Britney Spears or The Backstreet Boys. I think the writing quality is higher than that of some of the more well known music mags but not the best I've seen. Contrary to what the magazine's name might imply, AP isn't an underground publication.
Since there doesn't seem to really be an "alternative" music genre anymore, here's a short list of some of the artists they've had cover stories on:
There are more but I figured this would give a good idea
of what kinds of music they have articles
Some information here found at Alternative Press' website: altpress.com