Basically, it’s a “saddle-point” (flat spot) in the gravitational potential field for orbiting objects. At the L2 distance, the spacecraft “sees” the gravity of earth and sun added together, so it can orbit a million miles further from the sun than earth, but still take the same 365+ days to orbit the sun that the earth does. It’s a “cheap” (in terms of fuel) spot to hang out and still maintain (about) the same distance from earth at all times.
Oh, that’s a good explanation. So the sun is always on the opposite side of earth from L2 so both of their gravities combine to curve space enough for Web to hangout with minimal effort. Web’s orbiting mechanics I have yet to fully get. TY