NASA and other national space exploration organizations often use the gravity of objects in space to their advantage to save fuel. Often by slingshotting around planets and moons, you can use half the fuel you would normally, even if the distance is longer because essentially it's like gliding a bike downhill. Now some scientists have figured out a way to use gravity to create an incredibly efficient zone of interplanetary travel.

From PhysOrg:

The central concept is that of Lagrangian Points, or L-points. An L-point is a place in space where the gravitational fields of the surrounding bodies all cancel out to create a point of apparent zero gravity. This concept has been exploited before; the Solar and Heliospheric Observatory is stationed at one such point, where the close-by Earth's gravity cancels the distant Sun's gravity. It sort of just sits there, in this gravitational rut.

And that's basically what these gravity corridors are: they are pathways in space where the gravity is lowest and, in most cases, where the gravity is getting lower. If the gravity of the surrounding planets can be seen as big hills, the gravitational corridors are the sloping valleys between these hills. If scientists can find the valleys that slope in the direction they want to go, they won't need much fuel at all to just roll down those valleys.

Scientists in America and Germany are working to develop a map of these corridors for future space flights. They envision a time when very little fuel would be needed to easily drift from one of Saturn's moons to the other using the gravity of these floating rocks.