People work together in different ways. And they use a lot of collaboration tools: IP telephony for voice calling, web and video conferencing, voice mail, mobility, desktop sharing, instant messaging and presence, and more.

Unified communications (UC) solutions deliver integration of these tools, with seamless user experiences that help people work together more effectively. Anywhere, on any device. They bring real-time communication from your phone system and conferencing solutions together with messaging and chat, and integrate with everyday business applications using APIs.

UC solutions are available as on-premises software, partner-hosted solutions, or as a service (UCaaS) from cloud providers.

https://www.cisco.com/c/en/us/products/unified-communications/index.html#~solutions