Business telephone service has been around for many years, both as "on premise" and "off premise" solutions. Today's systems however are far more danced then even just five years ago. The reason why this is the case is because technology has really made a significant impact in the cost and availability of these types of solutions.
Some of the advances in technology that have evolved include the ubiquitousness of the Internet. This fact coupled with the stability of the Internet makes today's telephone systems for businesses inexpensive and easy to operate.
For example, the old business telephone systems, sometimes referred to as "PBXs" were very expensive solutions that required lots of hardware. Not only had that but the "on premise" phone systems required tons of wiring as well. Making matters worse, the telephone companies also charged businesses a monthly fee for the use of the service, making phone calls, and also maintaining and supporting the actual hardware. Furthermore, it often required a contractor to install everything at your location.