It gives you the choice of talking and listening from the base station as well as the handset. This great feature comes really handy in case you can't locate your handset. The number of channels a phone uses may vary from 10 to 40. The more channels a phone uses, the lesser is chance of interference from nearby hones and other remote devices. Batteries can be charged and used again and again.
Some units come with spare Battery and a spare battery charger.
In such phones keypads are either lit or glow in the dark for easy dialing in low light situations. Some phones with a built in speakerphone lets you call directly from your base without the handset. This facility lets someone at the base station talk to the person with the handset. Find the right place to put the base of cordless phone.