A property lien is a public notice that a creditor claims you owe money.
A lien affects you because it makes your title have a derogatory mark on it and in order to sell or refinance property, you must have clear title. To clear up the title, you must pay off the lien. This is why many creditors use this method—because whether the house is sold, or the owner is looking to modify the mortgage or refinance, they must clear the title in order to do that.