Being British, I will describe the British version of Robot Wars, although I believe the American version is a couple of years earlier.
Robot Wars is a television programme where members of the public compete against each other by building remote-controlled robots. The primary aim of each round is to destroy the opponents' robots whilst remaining intact yourself. As well as evading destruction from your opponent, you also have to ensure that you don't get toasted by the house robots.
Certain rules apply to try to keep things fair: robots have to be within a certain weight limit, and the following weapons are not allowed: projectile weapons, chemical or liquid weapons, electromagnetic weapons, untethered weapons (such as ball bearings). Apart from these restrictions almost anything else is allowed.
A wide variety of different shapes and designs of robot have been seen on the programme, with an even greater range of ingenious weapons. Due to the weight limit building a robot usually results in a trade off between armour, weaponry and speed, although the most effective shape is usually a wedge.
The first series of Robot Wars in the UK was presented by Jeremy Clarkson, better known as the smarmy sexist presenter of BBC motoring programme "Top Gear". He was later replaced by Craig Charles (Lister from Red Dwarf). Throughout the series they have been accompanied by the luscious Philippa Forrester, who usually struts around in a tight top and leather trousers and is at least as good a reason for watching the show as the robot battles.
The House Robots in the UK series can be quite fearsome.
The official website of UK Robot Wars is at http://www.robotwars.co.uk/