The fast, stable, and always free Linux RDP client
One of Remmina’s many features is a RDP client in the connection manager with many tunable options to get you connected just how you want
Remote Desktop Protocol - Wikipedia
Remote Desktop Protocol (RDP) is a proprietary protocol developed by Microsoft which provides a user with a graphical interface to connect to another computer over a network connection. The user employs RDP client software for this purpose, while the other computer must run RDP server software.