An umbrella term used to describe a style of
music that emerged in the late 80's and early 90's. Alternative
Rock is usually characterized by bands who have a "do-it-yourself" or non-conformist attitude; hence "alternative".
It originated with the jangle pop guitar sounds of R.
E.M. and the loud/soft dynamic of the Pixies and gained popularity when Nirvana brought it into the mainstream with their album Nevermind. Ironically, it became probably the most popular
music of the time period, which was a paradox of sorts in itself -- although purposely anti-mainstream and "against the norm", it became commonplace for
people to conform to non-conformity.
Today, the term is often thrown around by
people who don't really understand what it means and think that it can be applied to any band of their choosing. This is not true -- for a band to be truly Alternative, they have to follow the Alternative mindset; that is, they must either perform in a style of Alternative
Rock already established (see Grunge or Britpop) or be avant-garde and completely throw what it considered usual or average out the window.
The name is often wrongly associated with "Modern
Rock". This is wrong because whereas Alternative
Rock is a genre and follows a specific style, Modern
Rock is a radio format and simply refers recent bands.
Note: discrepancies with categorizing bands as "Alternative
Rock" come from the fact that most Alternative bands fit easily into an Alternative
Rock subgenre (Nirvana - Grunge, Modest Mouse - Indie) and can be classified as either the subgenre or "Alternative
Rock" in general; if a band covers more than one style instead of sticking to one in particular, they are usually just called "Alternative
Rock".