Disabling Weapons - reduces speed & accuracy of firing
* Probably right, though I think its damage and accuracy
Disabling comms - not sure, maybe affects your ability to order wingmen with damaged comms (useful for mission plots, though)
* Affects the ability to issue orders to that ship, if its damage to your own ship, it completely prevents issuing any order except rearm/repair. It also prevents you from hearing in-game messages, scripted or embedded.
Disabling sensors - affects ability to detect enemy ships, may also prevent beam fire (I believe sensors are required to fire a beam)
* I don’t believe it prevents beam-fire, but it will decrease sensor ability, such as ship tracking (ie not necessarily weapon accuracy, just chance that the turret will see you),
Disabling reactor - paralysyses weapons and engines IIRC. Fighters/bombers turns off radar.
* No effect – A scripted only event, used mainly for the Lucifer, but there is one on the Hatshepsut for some reason.
Disabling navigation - not sure... maybe affects speed of movement and use of waypoints.
* Fighters/bombers – causes inability to fire navigation thrusters, thus turn.
But like Aldo said, it is mostly events created in FRED. But things like engines and AWACS' sensors are hardcoded.