Through the phone's menus you can select whether you want to use traditional or en-bloc dialing when making calls. Your chosen setting is then applied whenever you use a phone that supports en-bloc dialing.
En-bloc dialing allows you to compose and edit the number to dial on your phone's display before it is sent to the phone system to be dialed.
With traditional dialing, when you start dialing a number on your phone, the phone immediately connects to the telephone system and starts passing the digits you dial to the phone system. You cannot correct the digits you have already dialed except by ending the call and starting over.