Remote Desktop Protocol (RDP) is a proprietary protocol developed by Microsoft, which provides a user with a graphical interface to another computer.
The protocol is an extension of the ITU-T T.128 application sharing protocol. Clients exist for most versions of Microsoft Windows (including Windows Mobile), Linux, Unix, macOS, Android, and other modern operating systems. By default the server listens on TCP port 3389.
Microsoft currently refers to their official RDP server software as Remote Desktop Services, formerly "Terminal Services". Their official client software is currently referred to as Remote Desktop Connection, formerly "Terminal Services Client".