You pick a character, then depending on your class, you can move far or short. When the bar runs out, you can't move, but you can turn your direction still. You can only shoot once per character turn, but you risk enemy counterattacks as well. When you move, you can be attacked by crossfire, but when the enemy moves, you can do the same back.
Its actually turn based gameplay, you move all your units, attack with them, then end your turn; then the enemy moves and its back and forth. But I'll be honest, I had a pain of a time in the later missions of the game, they really test your skill.