What is a mob exactly

Well a mob is a character who is not so important i think for example like a non-player character in the computer game.

you can also call then extras that I just in the background who have little to no importance at all

Oh okay thanks for the explanation ! At first I thought a mob was a delinquent so I was lost

You are welcome

wellll you're not wrong. In certain context mob can also me a synonym for mafia, and it can also mean a large crowd of people.

But in general when taking about a "mob character" in manga or anime the above definition (the one 'Oh my' explained) stands.

Thanks for the clarification ! I understand now :)