Looking for a clear explanation...

[Cross]

What I love about this, and SP in general, is that it gives me just enough science to decide whether or not to pull the trigger. Once I do there are a myriad of factors, not the least of which is random luck, that decides the outcome. It can be frustrating, but so is real life.

That's the way. A little science and plenty of intuition.

Hull Down

AFVs get a partial hull down by being on an elevation higher than the firer; making it harder to hit. It also causes less hull and more turret hits.

AFVs also get cover from being stationary in rough, rubble etc. or by entering a trench.

You can also 'dig in' a tank in an assault/advance battle.

That's about it I think.