[ Non-Alcoholic Drinks ] Open Question : Expired Milk???????????????

So i was brushing my teeth and realized that our milk is expired but it still tastes good, like it isn't expired. I started wondering where the expired milk in grocery stores go. I mean of course there isn't equal amount of buyers and milk for ALL to be gone. So does anyone know where the expired milk goes? Or do they do something to it so that it'll be better til the next expiration or something, IDONTKNOW!