Ignition timing is sometimes controlled by the distributor position. Ignition timing is set up to produce a spark at the perfect time. The ignition sets off the combustion mixture just before the piston reaches TDC (top dead center) so you get maximum power from the combustion process. In essence, you're turning the chemical energy of the gasoline air mix into mechanical energy. In order to do this effectively, you need to have proper ignition timing. The only time you should have to worry about ignition timing is if you have a distributor, and even then it's in question. Just because you have a distributor, that doesn't mean it's adjustable or that you should adjust it.
I want to say this about ignition timing: Don't adjust it. Unless you removed the distributor to perform some other repair, you should never have to set ignition timing. You can do more damage than good if you mess with ignition timing. If it's not right, you can cause detonation or pre-ignition, both of which can cause engine damage and a loss of performance.
Each engine has a specific procedure that needs to be followed when setting ignition timing. This is so often overlooked. Don't just grab the distributor and turn it till the engine runs well. Don't laugh; I've seen people do it, a lot. If you have a coil on plug setup or you have a coil pack assembly, your timing is not adjustable, so don't worry about it. If you think the engine is out of time on one of these engines, check the mechanical timing. These ignition systems run on mechanical cues. If the mechanical timing is off, it will also offset the ignition timing. This also means that if you find your ignition timing off, it could indicate a mechanical problem like a loose timing chain or belt.
In summary, if you suspect an ignition timing problem, check the mechanical timing first. Don't adjust the ignition timing unless you've done a repair in which the ignition timing was affected. If you do have to set ignition timing, make sure you follow the proper procedure. Improperly setting ignition timing can cause a loss of performance, or, worse, engine damage. Here is a video demonstrating how to set timing on a 1991 Acura Integra. This procedure will not apply to all vehicles, but you can use it as a guide to see how it is done and the tools that are used.