The Gulf Stream is a warm ocean current about 100 kilometres (62 miles) wide and 800 metres (2,625 feet) deep that runs from the Gulf of Mexico, up the coast of North America and across the Atlantic to the UK and eastern Europe.
It actually starts in west Africa as the Atlantic North Equatorial Current. In both directions, its power comes from the wind. Because the Earth is rotating, air currents tend to form large eddies, a little like the foam when you stir a cappuccino. North of the equator these cells rotate clockwise, which means the wind blows west in the tropics and eastwards atmid-latitudes.
As warm surface water from the Caribbean is cooled by the wind it also becomes saltier via evaporation, which makes it denser, so in the northern Atlantic the Gulf Stream sinks to become a southward deep-water current.
Answered by Luis Villazon.