This is just a visualization of gravity. The two green orbs are planets. The blue field underneath is space, which is curved by the planets like a trampoline. The red field is shows which way someone would get tugged by gravity as he rolls on the curved space. High points on the red field mean a person there gets pulled to the right. Low points mean a person there gets pulled to the left. points the touch the white/zero line mean a person there doesn't get pulled in either direction.
This is just a visualization of gravity. The point of this is to show that someone stuck between the two planets wouldn't get pulled apart by gravity (though he might get crushed by the planets). When the planets get close, he ends up stuck at the bottom of a gravity well, so he can't roll left or right down the slope of space. Gravity doesn't tug him left or right.
