The Lagrange points are points of equilibrium for 'small mass objects' under the influence of two massive orbiting bodies. This means these points are positions in space where the gravitational forces of a two body system like the Sun and the Earth produce enhanced regions of attraction and repulsion. These can be used by spacecraft (here the Webb is in consideration) to reduce fuel consumption needed to remain in position.
The James Webb Space Telescopes will orbit the sun 1.5 million kilometers away from the Earth, what is called the second Lagrange point or L2.The spacecraft will orbit Earth-sun Lagrange point 2, or L2.
L2 is a point located on the side opposite to the Sun, as it orbits the Sun. In this orbit, the Webb Telescope can maintain a safe distance from the bright light of the Sun, Earth, and Moon, while also maintaining its position relative to Earth.
See the image below where the Webb is located behind the Earth facing Sun.
