Parties thrown by the new occupants of a dwelling, to celebrate their assumption of occupancy. These are frequently held in shared houses, as a convenient excuse to get really drunk with new housemates. This is done by the new housemates partly in order to test combined and comparative reactions to their own debauchery. It also offers the opportunity to meet and potentially begin relationships with each other's friends.
'Housewarmings' are frequently held by students, or people newly graduated from university. Such housemates are often testing the boundaries of good taste and tolerance in their first domestic experience outside the homes into which they were born. They are frequently more turbulent and debauched than other parties, largely because they are mostly held in jubilant circumstances, by people who don't really know how bad they can be to each other yet. Older householders have housewarmings merely because they enjoy them.
Variants of the conventional 'housewarming' include the 'house-closing' or 'house-cooling' - held by house occupants who never got around to having a housewarming when they first moved in. These can be even more debauched than conventional housewarmings, due to the fact that the occupants will soon be leaving the house, and do not feel the need to think about long-term tidyness as they won't be around after the party is over. For this reason, in extreme cases, practices such as burning furniture, destroying interior fittings and so on can be quite popular - although such activities can be tempered by sanity in cases where the occupants are leaving a rented house, and a 'bond' is owed. If invited to a housewarming, it is important only to remember whether the house is rented or being bought by the house occupants before destroying anything.
Landlords and Estate Agents are not great fans of housewarming parties.