At a job interview I’d set up two different positions. My interviewer asked me to come up with a lesson plan, or at least something that they could learn from. After quickly introducing ourselves we set those up (see below). Black’s arrangement is the same in both diagrams, but White’s one differs a little. In one he’s already castled while in the other he’s not, and the c2 pawn is occupying the c4 square.
Black can play e5
If you know a little bit about the King’s Indian then you probably know why playing e7-e5 is fine here. White is controlling that square twice and you are defending it only once. However Black’s dark-squared Bishop is x-raying the h8-a1 diagonal. So if White goes pawn grabbing, Black will be able to play Nxe4, at the right moment, and get his pawn back with an equal position.
Black shouldn’t play e5
Why is Black unadvised to play that exact same move here ? Isn’t the g7 Bishop still there, ready to jump into the game at the right moment ? He surely is but White has castled and his c2 pawn is still on c2.