his first adds the new Player object to the array of players. Then it tells the table view that a new row was added (at the bottom), because the table view and its data source must always be in sync.
You could have just done [self.tableView reloadData] but it looks nicer to insert the new row with an animation. UITableViewRowAnimationAutomatic automatically picks the proper animation, depending on where you insert the new row. Very handy.