Voice over Internet Protocol, also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol networks, such as the Internet.
VoIP is the technology that converts your voice into a digital signal, allowing you to make a call directly from a computer, a VoIP phone, or other data-driven devices. Simply put, it's phone service delivered over the internet.
IP-PBX is a PBX (Private Branch Exchange) that switches calls between a traditional telephone user or between two traditional telephone users in the same way that a conventional PBX does but has the capabilities to switch calls over IP or VoIP (voice over Internet Protocol), and in most cases use Ethernet IP connections throughout the organization much in the same way that PCs connect to the LAN.
Software as a service (or SaaS) is a way of delivering applications over the Internet—as a service. Instead of installing and maintaining software, you simply access it via the Internet, freeing yourself from complex software and hardware management.
SaaS applications are sometimes called Web-based software, on-demand software, or hosted software. Whatever the name, SaaS applications run on a SaaS provider’s servers. The provider manages access to the application, including security, availability, and performance.
A Session Border Controller or SBC is a special-purpose device that protects and regulates IP communications flows. As the name implies, session border controllers are deployed at network borders to control IP communications sessions. Originally conceived to protect and control VoIP networks, SBCs are now used to regulate all forms of real-time communications including VoIP, IP video, text chat and collaboration sessions.