Positions in space where the gravitational pull of the two large masses precisely equals the centripetal force required to rotate with them.

The five gravitational balance points between two orbiting masses. The first Lagrange Point (L1) is in between the two bodies. more! and more

The points in the vicinity of two massive bodies (such as the Earth and the Moon) where each others' respective gravities balance. There are five, labeled L1 through L5. The first three lie along the centerline between the centers of mass between the two masses: L1 is on the inward side of the secondary, L2 is on the outward side of the secondary, and L3 is on the outward side of the primary. L4 and L5, the so-called Trojan points, lie along the orbit of the secondary around the primary, sixty degrees ahead and behind of the secondary. L1 through L3 are points of unstable equilibrium; any disturbance will move a test particle there out of the Lagrange point. L4 and L5 are points of stable equilibrium, provided that the mass of the secondary is less than about 1/25.96 the mass of the primary. These points are stable because centrifugal pseudo-forces work against gravity to cancel it out.

locations in space where the gravitational forces of two large bodies are equal. The first three points, L1 to L3, are located on the axis linking the two bodies. The other two points, L4 and L5, are on the orbit of the smaller body at 60 degrees on either side of the axis and are extremely stable.

Lagrange points (named for Josef Lagrange, the Italian-French mathematician who discovered them) are a set of five special points that occur between two large objects. At these points, a small orbiting object can orbit at a constant distance from both of the larger masses. This happens because at those five points, the gravitational force of the large objects is exactly equal to the centripetal force required to rotate with the objects. Three of the points are unstable (L, and L) and two are stable(L and L). Each of the stable Lagrange points forms an equilateral triangle with the two large masses.