1. For those who haven’t actually played some of the ancient FPS’s like Doom, or the more modern ones like Team Fortress 2, Rocket Jumping involves pointing a rocket launcher at your feet, jumping and firing the rocket launcher, using the explosion to propel you skyward. As these games use Wile E. Coyote physics, successful execution propels you in a graceful arc up onto otherwise unreachable platforms and ledges.
2. For those who haven’t actually played the Halo games, they use a more realistic interpretation of rocket splash damage, meaning successful execution of a rocket jump will propel small bits of you in a graceful arc up onto otherwise unreachable platforms and ledges. Thereby explaining the skulls found scattered around the various games in the most god forsaken places.