Look
Brown is beast titan and green is Armor titan and dude that fired the cAnnon is a human and anorther white stickman is attack titan

Beast titan ability is to throw rocks to its target very accurately like a sniper

Armor titan is cover with Armor which reduces the damage taken and is physically the strongest Titan

Attack titan ability is to summon spike from the ground to defeat his enemies and he can also use hardening ability which hardens his body and make him more stronger .I will show you hardening ability in part4 or 5

With this said I hope you understand the story more nicely also attack titan and beast titan are team vs Armor titan and cart titan.cart titan is the one you saw in part 2 wearing black Armor