Mike Gabriel, involved in maintaining packages with Qt and Mate on Debian,
Unity 8 uses the Qt5 library and the Mir display server, which acts as a composite server based on Wayland. In combination with the Ubuntu Touch mobile environment, the Unity 8 desktop may be in demand to implement the Convergence mode, which allows you to create an adaptive environment for mobile devices, which, when connected to a monitor, provides a full-fledged desktop and turns a smartphone or tablet into a portable workstation.
Source: opennet.ru