How does cover work? They never really explained it in the game, and there's nothing about it in the help.
Does being in cover reduce my chances to be hit? Do I take reduced damage? Does it affect my aim/damage? Can I shoot over full-cover, or only around it (like in X-Com)? Do partial- or full-cover block Line-of-Sight? How do I know if I'm flanking or being flanked (does such a concept even exist)? Why do I sometimes get a no-cover icon in a seemingly-valid, non-flanked position?