As the names suggest they implement a Client respectively a Server API for the Wayland protocol. The API is Qt-styled removing the needs to interact with a for a Qt developer uncomfortable low-level C-API. For example the callback mechanism from the Wayland API is replaced by signals; data types are adjusted to be what a Qt developer expects, e.g. two arguments of int are represented by a QPoint or a QSize. WWW: https://api.kde.org/frameworks/kwayland/html/index.html