In order that the phones are not confused, you can give them a name (living room, up / down etc.), which will then be displayed permanently on the screen.
Otherwise, it has (up to the answering machine) almost the same functions as the base station, it can be up to 100 numbers / names in the phone book and it has the same (terrible) ringtones.
Internal calls to / connect naturally goes well and the answering machine can listen via speakerphone on the handset. If new messages are there, an icon appears on the display when the answering machine is not in range (as with us - one floor up) is super convenient.