Lock on with rockets : FPS / MMORPG / RTS Discussion

To lock on with rockets, target a person, vehicle, etc., then hold R until it says that it is locked. The red reticle will follow the item. Release R to fire.
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While using a rocket launcher, you can lock-on to the following items: turrets, vehicles, and the Phantom's plasma cannons (Covenant Dropship's turrets). To lock-on to those objects, aim your cross-hairs at the object. By doing this, your rocket launcher's cross-hairs should have four red squares on the corners. Then, hold Fire so that the rocket launcher will fully lock-on to the object. While this happens, the lock-on system of the rocket launcher should make a few repetitive beeping sounds. After the beeping sounds have ended, the cross-hairs should be completely red and ready to fire. Release Fire and your spiraling heat-seeking rocket launcher missile will go to the target.

What is this? This is just general information that all players who have played the game would know.