Telecom generally runs in several flavors: Digital circuits and phone systems, Analog the same, and VoIP. Some systems can operate with all technologies simultaneously. I have several systems like that. VoIP can be hosted (system is in the cloud), or a local VoIP server that handles all the connectivity. We can also create systems that operate across those variants.
Multi-Site refers to your company having multiple offices, but wanting easy communication among them. Example, I have a client with their HQ in Chatsworth and another building in Santa Ana. Right now, they have two phone systems and if someone calls one and needs the other, they have to hang up and call the other location. Another client has HQ in DTLA and another in Pasadena, with plans to go nationwide. All easily handled.
CRM integration can be tricky. If they have some CRM database and want to have click-to-call or screen pops on inbound calls so the client record opens as soon as the call rings so they can get right down to business, the integration makes it happen. It can be tough, but we try our best.