A housewarming party is a party held on the occasion of moving into a new residence. It is an occasion for the hosts to present their new home to their friends, and sometimes for friends to give gifts to furnish the new home. Housewarming parties are generally informal; usually there are no planned activities besides a possible tour.

Welcome to my house warming party on Saturday. OPM*!
*OPM: oma pullo mukaan, i.e. bring your own booze. A Finnish expression that is used in an invitation. If service is limited to beer, cider and non-alcoholic beverages, the invitation may encourage people to bring their own alcoholic drinks with them.

A house cooling party is a party to celebrate moving out of a place. Opposite of "House Warming Party". Instead of guests bringing gifts for your new home, they can be given things you want to get rid of.
“We're moving out of our place next month, so you're invited to our house cooling party this Saturday. Please bring your own bag, and be prepared to go home with some lovely parting gifts.”
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