gdm provides the equivalent of a "login:" prompt for X displays- it pops up a login window and starts an X session. . It provides all the functionality of xdm, including XDMCP support for managing remote displays. . The greeting window is written using the GNOME libraries and hence looks like a GNOME application- even to the extent of supporting themes! By default, the greeter is run as an unprivileged user for security.
