Envy-free item allocation

Envy-free item allocation is a way to fairly distribute things among a group of people. Imagine a group of friends playing a game where each of them gets a surprise gift box at the end. Envy-free item allocation makes sure that each person in the group gets a box with something they're happy and excited about, so that nobody will feel envious of what someone else got. In more mathematical terms, envy-free item allocation means each person looks at the other person's items and agrees that they would be just as happy with the items they were given.