Microsoft Lync is an integrated multi-platform enterprise communications suite designed to work alongside Microsoft's Office 365 Enterprise plans. The basic feature set for Microsoft Lync includes instant messaging, VOIP telephony and video conferencing, with all features available in a single interface. Companies may purchase client access licences (CAL) and pay for use of a third-party Lync server or may purchase both CAL's and 1 (or more) Lync server licences.
One of the major selling points for Microsoft Lync is that it incorporates all business communications into a single interface which can be accessed on both PC and Mac, not to mention iOS and Android devices. Incorporating text, voice and video communications into one client application cuts costs and hypothetically increases productivity. Another of Lync's advantages is its integration with Microsoft's Office 365. Microsoft makes it easy to share Office files, but perhaps the most useful tool is Lync's integration with Outlook. Lync has access to all of the contacts stored in Outlook as well as planned video conferences or conference calls.
Although one of Microsoft Lync's primary three features is VOIP telephony, this feature is strictly limited to voice communications between computers; you can't dial a telephone number and connect over the traditional telephone network like you would expect to be able to with a hosted PBX or cloud-based PBX system. At first glance, Lync appears to be an all-in-one solution for business communications, and it certainly is for the most part, but it deals exclusively with Internet-based communications. There are Gateway's available from companies such as Audiocodes that will bridge between the Lync server and a 3rd party IP PBX however you do not get a rich feature set between the two. Since most - if not all - businesses still need to make phone calls to other non-IP phones, companies that buy into Lync will likely be left with a business telephone system that is sub-par in comparison, unless they also want to purchase a hosted PBX system, however this is a separate cost.
The lack of an option to fully incorporate a PBX system into Microsoft Lync is its most salient shortcoming. It is marketed as an all-in-one business communications solution but it isn't quite possible yet to completely ditch the traditional telephone system, at least not in a business environment. Overall, Lync is a great business communications client, but only for online communications. Looking to the future, this sort of system will become more and more prevalent, but a fully online communications client is not widespread enough yet to suffice alone, without accompanying traditional telephone systems.