What is VoIP? - VoIP stands for Voice Over Internet Protocol. Traditionally, when you make a phone call, it travels via PSTN (Public Standard Telephone Network) however, nowadays, it is increasingly traveling via the internet. When voice traffic travels via the internet, it is then when it is described as VoIP. This, of course, is a highly simplified version of the process. For more details, you can consult the Voice over IP wikipedia. Since VoIP is becoming more and more reliable and cost effective, it is getting widespread acceptance in the mainstream.

What is Sip? - Sip stands for Session Iniation Protocol. Its now primarily the protocol of choice for VoIP communication. There are others such as H.233

What is a Sip Phone? - It allows you to make a phone call using Sip protocol. Most Sip phone plugs into an Ethernet port.

What is a Soft Phone? - A soft phone is a computer application that enables users to make telephone calls directly from a general purpose computer using VoIP. With a soft phone, one can make a call from a PC to a phone line, from a phone to a PC, or from soft phone to soft-phone on different PCs

What is an ATA? - ATA means Analog Telephone Adapter. Most home and office phones, use analog signaling to communicate with your local telephone company’s switch. An ATA converts analog signals into VoIP so that calls can traverse the Internet.

What is a DID? - DID stands for Direct Inward Dialing. In simple terms, its a phone number assigned by VoIP providers such as Voip carrier to allow you to connect to the PSTN (Public Standard Telephone Network), so that you can receive phone calls.