Ubuntu server and desktop are two different versions of the Ubuntu operating system, with the main difference being their intended use and interface. Ubuntu desktop is designed for personal computers, with a graphical user interface and pre-installed software for everyday tasks like browsing and word processing. Ubuntu server, on the other hand, is designed for servers, with a command-line interface and no graphical desktop, it's meant for running services and applications on a network. For beginners, Ubuntu desktop is generally easier to use and more user-friendly, while Ubuntu server requires more technical knowledge and is better suited for those who need to set up and manage a server.