I'll explain thusly;
Soldier A is carrying a missile launcher, loaded with a laser-guided missile.
Soldier B is carrying a laser painting unit.
Soldier A is behind a fence, and can't see over it to hit an enemy in a building on the other side.
Soldier B can see the enemy in the building, and takes careful aim with his laser painter.
With the target painted for Soldier A (specified for the launcher Soldier A is carrying during the painting action), A points his launcher up to fire over the fence - but not so high the missile can't correct itself.
The missile zips up over the fence and locks in on the 'tag' painted for it, adjusting it's course for a more direct hit. Enemy in the building recieves a missile to the face.
What's the catch with missiles? Well, they shouldn't be able to alter course very quickly, and should be incapable of adjusting course by more than 45~ degrees either way of their target - so no looping behind you or anything - though this is up to the weapon's creator. Also, they pack a lot less punch than rockets. Rockets are just self-propelled explosives. Missiles have to adjust their course to be able to strike their target more accurately, and thus space must be devoted to the guidance systems, taking away from the overall payload.
"Heat" Seeking Missiles - HSMs track the nearest sufficiently hot object - usually locking onto the heat signatures generated by flying units. They can be distracted by fire, however. HSMs are heavier than LGMs, but do not require a second soldier to paint the target. If it can't find a target (bodies are too cool for an HSM to follow, really) then it acts as a rocket.
Laser-Guided Missiles - LGMs use a painted target, like the above example. LGMs cannot home in unless they have a target painted for them, but are more accurate than the standard HSMs. If launched without a target, LGMs act as rockets. LGMs are fairly light as they have a simple tracking mechanism, but due to their dual-soldier requirement they are somewhat more tricky to field and use effectively.
Wire-Guided Missiles - WGMs are guided by the launcher operator. They act as rockets but are a fair sight more accurate; they attempt to home in on whatever was targeted. WGMs can't really be fired blind/unguided as they just home in on the targeting reticle, and launching a WGM uses a lot of TUs. WGMs are also the heaviest of the missiles.
Edited by Exo2000, 12 August 2007 - 11:53 PM.