X Window selection

Selections, cut buffers, and drag-and-drop are the mechanisms used in the X Window System to allow a user to transfer data from a window to another.  Selections and cut buffer are typically used when a user selects text or some other data in a window and pastes in another one. Drag-and-drop is used when a user selects something in a window, then clicks on the selection and drags it into another window. Since the two windows may be handled by two different applications, these mechanisms require two different clients connected with the same X server to exchange data. The X Window System core protocol includes some requests and events that are specific to selection exchange, but the transfer is mainly done using event sending and window properties, which are not specific to selection transfer.