what is l1 point

A Lagrange point is a position in space where the gravitational forces of a two-body system, like the Sun and the Earth, produce enhanced regions of attraction and repulsion. There are five Lagrange points, labeled L1 to L5, and each has unique properties and uses. The L1 point of the Earth-Sun system is the point where the gravitational attraction of the Earth and the Sun combine to produce an equilibrium. It lies on the line defined between the two large masses and affords an uninterrupted view of the Sun. The L1 point is currently home to the Solar and Heliospheric Observatory Satellite SOHO. A spacecraft at L1, L2, or L3 is meta-stable', like a ball sitting on top of a hill. A little push or bump and it starts moving away, so a spacecraft must use frequent rocket firings to stay in so-called 'halo orbits' around the Lagrangian point.