Any tool that is used to communicate and collaborate is important.  Each tool’s importance is different to different users, based on individual work flows and daily tasks. However, our top 5 most important features of unified communications are:
Video and audio conferencing
Enterprise voice and mobility
Presence and messaging
Calendar scheduling
Screen and file sharing
Bringing these features under a single application, or a “single point of truth,” such as Microsoft Teams, enables users to achieve common tasks without having to switch applications.  This is the most important unified communications feature, is that all tools can be integrated into a single application.