What is the difference between left and right wing?

The terms left and right wing refer to the political spectrum, usually expressed in terms of a line with the far left and one end, the far right at the other, and the centre in the middle. 

In British politics, the Labour party are considered centre-left, with the Conservatives correspondingly centre-right. The Liberal Democrats occupy the centre, while UKIP are further right, and the Green party further left. 

The left and right wings differ on many things, but most importantly on the role of the state. The left believes the government should play an active role in regulating the economy and providing welfare (NHS, benefits). The right support a smaller state, with a greater role for the free market and business.