An IP PBX provider offers an Internet Protocol (IP) based Private Branch Exchange (PBX) system that allows businesses to manage internal and external phone calls over the internet, instead of traditional telephone lines. It provides features like call forwarding, voicemail, conference calling, and more, all powered by VoIP (Voice over Internet Protocol) technology.

A VoIP gateway, on the other hand, is a device that connects traditional telephony systems (like PSTN lines) to an IP-based network. It converts analog voice signals into digital packets and routes them over the internet, allowing businesses to integrate older phone systems with newer VoIP technologies.

Together, the IP PBX and VoIP gateway work in tandem to streamline communication. The IP PBX handles internal call management and features, while the VoIP gateway connects your business to external phone networks, enabling seamless communication between VoIP and traditional phone systems.