If you are looking for your business to be accessible from wherever you are, whether it be in the office, at home or in a meeting. Unified Communications is for you. If a client/customer calls you it could ring both your mobile and landline, if you get a voicemail it could then send that voicemail to Outlook so you can listen to it from your PC/Laptop, or if you have a mobile with access to email you can listen to it on the mobile as well. Throw in Lync with this (now Skype for Business) and the ability to dial from it then it all starts to look a bit seamless.
Unified Communication allows individuals to send a message on one medium, and receive the same communication on another medium. Therefore you can receive a voicemail message and choose to access it through e-mail or your mobile . If the sender is online according to the presence information and currently accepts calls, the response can be sent immediately through text chat or video call. Otherwise, it may be sent as a non-real-time message that can be accessed through a variety of media.