The far side of the Moon is the lunar hemisphere that always faces away from the Earth, opposite to the near side.
One key difference between the Moon's far side and its near side is the difference in topography. Compared to the near side, the far side's terrain is rugged, with a multitude of impact craters and relatively few flat and dark lunar maria. One commonly accepted explanation for this difference is related to a higher concentration of heat-producing elements on the near-side hemisphere. Some newer research also suggests that heat from the Earth at the time when the Moon was formed is the reason the near side has fewer impact craters.
About 18 percent of the far side is occasionally visible from Earth due to libration. The remaining 82 percent remained unobserved until 1959 when it was photographed by the Soviet Luna 3 space probe. An interesting proposal that has come about recently is to install a radio telescope on the far side so that the Moon can shield it from interference from Earth.