Unowned property is something that nobody owns. Just like how some toys at the park don't belong to anyone and anybody can use them. Sometimes this happens with houses, land or things like a bicycle that have been left unlocked and nobody claims ownership. It's not a good idea to use or take unowned property without asking first because it's important to respect other people's things and also because it might belong to somebody who just hasn't come back to claim it yet. It's important to be honest and return the property to its rightful owner if possible.