A legal document that protects the buyer from all legal claims or outstanding debts against the property they are buying. If there are any after the closing, the buyer will not be financially responsible. Instead, the seller will be and if anything prevents the deed from transferring to the buyer.
For example: If you receive a bill from an exterminator disclosing, they have not been paid for a job they have done on the property before you bought the house, do not worry. The previous owner is liable for that bill because of this warranty so it is beneficial to have.