Whats a tanks job?

Um is there another defenition for a tank? Tanks can get kills, but their main focus is to engage high priority targets so teamates can sweep in and sweep up.

tanks throw down cc to make it easier to kill their target. a stunned kog maw is a dead kog maw. they also want to position themselves to frontline for the carries on their team, so its more "threatening for that tank to be on your face, im going to attack the tank, instead of the carry thats a bit over there." thus resulting in the enemy team dealing less damage, thanks to the armor/mr of the tank.

I suggest you watch this video https://www.youtube.com/watch?v=MGEACUusvyA. His voice is difficult for some to handle as he has stated he has a speech impediment, but he is quite knoweledgable in the game.