The biggest characteristic the distinguishes itself from other rock is the fact that while "traditional" rock music uses a 4/4 meter, math rock uses time signatures such as 7/8 or 13/8, among other "asymmetrical" meters. It gets it name from its "mathematical" character.
Its influences derive from bands of the 60s and 70s such as Genesis, Jethro Tull, Yes, Rush, and Pink Floyd but also draws its influences from heavy metal and punk rock as well as this "progressive rock" acts.
Lyrics are very rarely focused on in math rock and often in recording, vocals are lower in the mix.
Chicago became a central hub for "math rock" in the 1990s with bands like Big Black and Shellac, as well as other bands on the Touch & Go and Quarterstick labels.
Pittsburgh, PA is also considered a hub for "math rock" with bands like Don Caballero who blend heavy noise rock with jazz influences.
Other notable bands in the "math rock" genre are Shudder to Think, Jawbox, A Minor Forest, The Dillinger Escape Plan, June of 44, Meshuggah, and Nomeansno.