Here in Washington, the Seller Disclosure Statement is required by law. Most sellers (with a few narrow exceptions) must complete and provide one to a buyer. Upon receipt, the buyer has three days to rescind the contract and walk away from the purchase (with a return of the earnest money, of course). If you're looking for a free copy to use, find one here.
This form is most commonly called the Form 17, because that is the designation given it by the Northwest Multiple Listing Service. The law requires specific language, so the terms - and forms - are interchangeable.