Meaning
A face with its mouth wide open in a wail and two streams of tears pouring from closed eyes. It literally means sobbing, but in everyday chat it is just as often used for overwhelming feelings of any kind, including laughter and joy.
People send it when something is unbearably cute, painfully funny or deeply moving: “The puppy fell asleep in his food bowl 😭” It also works for dramatic, half-joking despair about homework or a canceled show. Because those meanings are opposites, add a word or two when the situation is truly sad so the other person does not think you are laughing.