Peter Garant says:

This is how VoIP works; you contact a service provider, and they will give you an adapter. You, or a technician can place the adapter on your telephone. If you prefer, you can link all the phones in your residence so that they are all VoIP enabled. The best thing is that there is no need to upgrade your phones. Just put in the adapter, and you can start using it.

Almost all VoIP service providers also provide the functions that traditional phones do, such as caller ID, voice mail, three way calling, repeat dialing, forwarding etc. The only difference is that with VoIP the costs are reduced.

Some even provide toll free numbers, fax service and options for linking up your laptop so it can be used with VoIP.