Strafe Jumping is an exploit commonly used by players in the Quake series to allow the player to move at a faster rate. This technique is highly implemented in Deathmatches or Speedruns since it allows the player to rapidly travel around a map. With this significant increase in speed, players who master this technique are able to gather Weapons and Ammo at a much faster rate than the inexperienced player. Furthermore, the acceleration makes it so that a player is harder to hit, though the player Strafe Jumping must also become accustomed to the increased rate of movement in order to hit another player. It is advised to use a weapon with Splash Damage such as the Rocket Launcher to allow for a greater margin of error.
When moving forward and backward, a player is limited to a certain speed. This limitation is removed by combining a forward motion with strafing in the direction that the player wishes to go. As the player will be strafing, it is advised to start at a 45° degree angle from where they intend on traveling. Once the player has temporarily increased their movement through strafing, their speed can be maintained through jumping. The player must time the jumps immediately upon hitting the ground in order to continue moving at an accelerated pace. Furthermore, a player can further increase their speed by turning in the direction that they are hopping, though these movements must be relatively smooth (jerky movements will result in deceleration).
You can read a simple but effective Strafe-jumping guide in Holysh1t. Featured video recorded with vQ3A physics.
Bunny Hopping is an advanced form of Strafe Jumping that requires more actions to successfully perform the maneuver. Depending on the particular game, the player may be required to Bunny Hop to gain the benefits normally obtainable through Strafe Jumping. For example, Quake does not give the player a speed increase through Strafe Jumping, meaning players must instead Bunny Hop to gain the benefits of the exploit. The main difference between the two is that Bunny Hopping requires the player to release the forward movement key immediately upon strafing. Due to the similarity of both types and the fact that it generally depends on the game as to whether Strafe Jumping or Bunny Hopping is used, it is extremely common for players to intermix the terms.
While Strafe Jumping is a skill that can be mastered to be better in competitive play, John Carmack has stated that the characters are expected to be similar to action heroes such as Arnold Schwarzenegger or Sigourney Weaver. By traveling down corridors whilst hopping like a rabbit, Carmack feels this goes against the intent of the games. Carmack has wished that players would focus on running and dodging, instead of hopping from place to place. Though he tried to get rid of Strafe Jumping in Quake III Arena, doing such also caused running to become awkward, the side-effect resulting in the fix being reverted and the exploitable bug being left in the game .