When each of the guests at a party brings a dish for everyone to share, that's a potluck. If you're invited to a potluck, you might want to bring your famous macaroni and cheese.
This North American noun describes a particular type of meal, sometimes called a "covered-dish-supper" or a "dish-to-pass." If someone asks you to come to a potluck or a potluck supper, you'll want to be sure you don't arrive empty-handed. The potluck's origin dates to the Great Depression of the 1930s — earlier, the word meant "the luck of the pot, or food for an unexpected or uninvited guest."