The sale is formally ended at the closing table. In most transactions, the closing lasts less than an hour and often occurs at the title companies office. You and the title companies officer or escrow agent will preside.
The sale actually consists of two transactions: 1) transferring the property to the buyer and 2) paying off the existing mortgage on your home (or allowing the buyer to assume your mortgage). To transfer the property, the title company will present documents proving that you have the title. Proceeds of the sale may be disbursed at closing or shortly thereafter, once all paperwork and verifications has been processed. When you give your house key to the new owners, the sale is completed.