A space station is a scientific laboratory inhabited by humans that orbits around the Earth.
Currently the only operational space station is the International Space Station (ISS), although the space program of the USSR, and later the Russians had 6 Salyut Stations, and later the station Mir. The American Space Program put aloft Skylab in 1973 atop the last Saturn V rocket, and was serviced from the same command modules as were used in Project Apollo. Skylab orbited the earth until 1979 although the last manned flight was in 1974.
In science fiction, space stations have been used extensively, including Star Trek: Deep Space 9, Babylon 5 as well as in many novels.