The Big Dipper is an asterism, a recognizable pattern of stars, within the constellation Ursa Major (the Great Bear). The two stars at the end of the Big Dipper's "bowl" are known as the pointer stars. If you draw an imaginary line through these stars, it will point you directly towards Polaris, the North Star.
This is a helpful trick for navigators, as Polaris is always located in the northern sky, marking true north.
