How can you tell the difference between rock music and alternative music?

Answer 1

Alternative rock is a kind of Rock Music, so, there is no difference. There's no such thing as just plain, "rock music," rather, there are dozens of different sub-genres: early rock, folk rock, psychedelic rock, classic rock, punk rock, glam rock, heavy metal, grunge, alternative, etc. And many of the sub-genres have their own sub-genres, like, thrash metal, black metal, progressive metal, Viking metal, speed metal are sub-genres of heavy metal, and proto-punk, post-punk, punk pop, hardcore punk, British punk, New York punk are all sub-genres of punk music.

All of these sub-genres and sub-sub-genres can be called "rock music." Like, you can say that Nirvana is a rock band, or, you can be more specific and say they are a grunge band. You can say that Black Sabbath is a rock band, or, you can be more specific and say they are a heavy metal band. Or, you can say the Ramones are a rock band, or, you can be more specific, and say they are a punk rock band.

It's sort of like, there's green M&Ms, red M&Ms, blue, orange, yellow, and brown M&Ms, but there are no "plain" M&Ms.

See the Related Link below for the Wikipedia entry on alternative rock.