VNC

VNC stands for Virtual Network Computing. It is, in essence, a remote display system which allows you to view a computing environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures.

Proxmox VE uses VNC to provide access to virtual machines using the web-based noVNC client (which is independent from a possibly installed VNC server inside a virtual machine), that means no special client software has to be installed, a web-browser is sufficient.

In exceptional cases it may be requested to use another client software, look here for more information.