What is a quitclaim deed? Does it change the owner of a property? What can it be used for?

A quitclaim deed releases whatever interest the grantor(s) has in the property to whomever is named in the deed as the grantee(s), it just doesn't contain all of the covenants associated with a warranty deed. So, if you owned a house and signed a quitclaim deed over to John Doe, then you are giving whatever ownership interest you have in the house to John Doe. If someone had you sign a quitclaim deed over to them, it is probably because they believe you have some claim to the property and they want to extinguish that claim in favor of themselves. Especially when dealing with something as significant as real estate, don't sign anything that you do not completely understand.

Your executing a Quitclaim Deed is you "giving" not "getting".

The "Buyer" does not sign a deed. The "Seller" does. Thus, if you signed a deed, you likely conveyed property to a third party. A quitclaim deed is a type of deed in which you convey property subject to all encumbrances - you do not make any warranties that the land is free of liens, easements or other restrictions.