A wind turbine is a single unit, which looks like an airplane propeller on top of a long stick. It transfers energy from the wind into rotational motion, which it then transforms into electricity by the use of a generator. A single turbine may be used to provide electricity to a group of houses or buildings, and smaller turbines may be used for an individual home or building.
A wind farm is a collection of these wind turbines in a given location, used collectively for the generation of electricity. A wind farm is often a very large installation, which can be hundreds of square kilometers in area, and provide electricity to the electrical grid for people to use.