In the vicinity of two bodies in space that orbit each other lie five Lagrange points, named after Joseph-Louis Lagrange, the French / Italian mathematician (1736-1813). Lagrange made major contributions to various branches of mathematics, and discovered the Lagrange points in 1772 while working on the three body problem, first described by Sir Isaac Newton in 1687.
The diagram at the left shows the location of the five points. The Earth-Moon system has five Lagrange points, commonly labeled EML-n, and the Sun-Earth system has five points, labeled SEL-n:
Wikipedia has an excellent article on Lagrange points in space.