Unified Communications (UC) is the convergence of multiple types of communications including real-time communications such as telephony and instant messaging and message-based communications such as email and voicemail.
Unified Communications also integrates multiple media types including voice, video and data.
In a Unified Communications environment all these types of communications are accessible from a single user interface. This might be a desktop client application or a single handheld device (e.g. smartphone or tablet).