Mortgage
A mortgage is the security the bank takes over the financed property: if the borrower stops repaying the loan, the bank can have the property sold to recover what it is owed.
It is created by notarial deed, usually on the same day as the purchase deed, and then entered in the public register. The buyer remains the full owner and can sell the property: the mortgage simply has to be released, most often using the sale price.
Setting it up incurs costs (duties and notary fees) that add to the purchase costs and must be budgeted for.