What were the features and the purpose of the tank used in world war 1?

Well for starters say for ex: Hey we are about to go to WAR with team red, as team blue we need lethal weapons and more men, so after that's done lets go to WAR, ''Oh no they have weapons and we don't, run lets go'' -Blue leader, so its obvious the tanks we're there for many purposes, to fire explosives at the enemies for starters to kill one another and destroy each other, and also to protect themselves like a shield, also for transportation in lands, and features, I would say long distance shooting aim, and strong metal to withstand other metal. And also to search for other enemies as well. *Below is a pic of a tank from ww1, I found it off google and take no credit for it.