Jumping in Combat Arms is a way of propelling the player character off the ground momentarily. When the player presses the space button (or whichever key the player has bound to Jump), the character pushes their feet off the ground and is elevated in the air, from half a second (jumping on the same elevation) to even three seconds (jumping from a high elevation to a lower one). Jumping enables players to get to a point where a character can't manually get there by walking, like getting on top of a crate.
Jumping, however, decreases Accuracy greatly on one's weapons, and jumping off a very high level to a lower one leads to Falling, damaging or killing the player. Bunny Hopping is a tactic requires large amounts of jumping and movement to prevent enemy players from easily acquiring the player as a target at close ranges. Enemies can easily spot jumping players because the player is simply showing him/herself by going up and down frequently.
Currently, no item offers any statistical "Jump" bonuses.