It's good to ask permission before doing things.
Mark has started a new job in an office.
Mark wants to eat lunch.
Mark asks a coworker if he can have their chips in exchange for bringing them a snack tomorrow.
Mark eats a coworker's chips in the break room while they're working.
Mark's coworker knows where their chips went and takes up the offer.
The coworker has no snack and doesn't know where it went.