You use your phone system (also known as a PBX) every day, so you already know that phone systems are responsible for handling your call control and managing your connection to your telephone service provider. What you might not be familiar with is VoIP.
VoIP is short for Voice over Internet Protocol. VoIP is a way to make calls across your Local Area Network (LAN) and or Wide Area Network (WAN). The technology behind VoIP converts your analog voice into digital packets which are then sent across a network using the Internet Protocol (IP) to their end destination. VoIP is most commonly associated with making calls across the Internet.
As you've probably guessed, a VoIP phone system gets connected to your LAN. It uses your LAN as the backbone of the system – connecting your VoIP phones and your VoIP service provider to the VoIP PBX. That makes a VoIP phone system a phone system that uses IP technology to handle your call control and manage your connection to the Wide Area Network over which your VoIP service comes.
Even though a VoIP phone system uses VoIP and is connected to your LAN most systems can connect directly to the Publicly Switched Telephone Network (PSTN). This gives you the ability to use both VoIP and the PSTN for your calling.