It's inconsiderate to steal someone else's lunch.
Jenny is taking her lunch break in the break room at work and forgot her lunch, but see's her co-worker Alex has a big salad in the fridge.
Jenny wants to eat.
Jenny asks Alex if he would mind giving her some of his salad.
Jenny takes Alex's salad and begins eating it, then Alex walks in and catches her.
Alex is happy to help Jenny and shares it with her.
Alex is angry because now he has nothing to eat, and he knows Jenny stole from him.