In theory alternative rock is supposed to signify rock music that is alternative from the mainstream. However, mostly thanks to Nirvana, the sound of alternative rock has become so hugely popular that it is capable of selling millions and being mainstream itself. For some, alternative rock is mostly synonymous with post-grunge, while the British prefer to use the term indie (rock) to distinguish alternative rock that is not post-grunge.

Alternative rock can only realistically be traced back to the 1980s – although artists from the 60s and 70s such as the Velvet Underground, Neil Young and Television may sound similar to alternative rock, the term was first used to describe mid-80s independent rock bands such as Sonic Youth, Husker Du, R.E.M., The Jesus & Mary Chain, the Violent Femmes, The Cure and Pixies. Here there is a strong overlap with what is also called college rock due to the listenership mostly comprising college students.

The late 80s saw an alternative rock subgenre called grunge gain in popularity in the Seattle area. Bands like Soundgarden and Nirvana soon achieved worldwide fame, and Nirvana’s second album Nevermind (1991) effectively changed the meaning of alternative rock forever. Its massive critical acclaim and huge worldwide sales took alternative rock into the mainstream, from where it became reasonable to ask “alternative to what?”. Combined with similarly heavy rock albums like Pearl Jam’s Ten, the Red Hot Chilli Peppers’ Blood Sugar Sex Magic, and the self-titled debut from Rage Against The Machine (1992), alternative rock attracted enough fans to put it firmly mainstream.

Alternative rock radio stations continue to focus on early-to-mid 90s post-grunge -- a.k.a. Nirvana and everything after –- so alternative rock, in a broad sense, is now pretty much synonymous with ‘rock from the last 20 years’. More specifically, hugely popular bands like the Foo Fighters and Nickelback can both be accurately described as either alternative rock or post-grunge.