the timing we are talking about here is the ignition timing
like Bruce pointed out, you can get a timing light
it has 3 wires (a positive and negative that go the battery and a signal wire which clamps on the #1 plug wire)
inside the timing light is...you guessed it...a light
when the engine is running the signal wire will pick up on the spark traveling through the #1 plug wire and will trigger the light
if the gun is aimed at the harmonic balancer it will reflect off the timing mark and by looking at the dial cast into the waterpump you can see what your ignition timing is
camshaft timing, when and how for which valve opens is something we can NOT see from the outside (I think that's where the confusion came from)