There are 3 different types of zombies in the current state of the game.

Standard Infected
The standard infected only have two moves, attack and grab. Attacks will deal one heart of damage to a human player, and will knock the human back. The grab can be used on any human without armor, but has a cooldown. Once a human is grabbed, they can be thrown very far. The most common strategy right now is to throw a human into a body of water to leave them slow and defenseless. But you can also use grab on explosive barrels. Throwing these towards a human will send them flying. This is vital for getting humans off of high ground, or throwing them off of their intended path. A good barrel can get humans killed.

Bombers
Ooooh bombers, these guys are really god damn dangerous. If you hear rapid beeping and see a yellow warning sign, you need to get the hell away from wherever you are. A bomber within melee range will deal three hearts of damage. That's an instant kill on a human without armor. The only real way to deal with bombers is to either shoot them until they're too far away to do any damage, or to run. If you're the bomber, though, you have a lot of opportunities for kills. The best strategy is to flank and charge in, with your timer already ticking, while the humans are preoccupied.

Phantoms
I don't know much about these mime lookin' mothers, to be honest. They can turn invisible. They're not too dangerous. If you hear some beeping but you don't see a zombie nearby, just gunjump away.