Ldm is an X11 display manager similar to xdm, gdm and kdm, but unlike those it wraps the X11 traffic within an SSH tunnel to provide a secure login mechanism for remote X sessions.

This package includes the server components used by ldm to discover available sessions and locales on the server. It also recommends packages relevant for local device access, a login session, and remote sound.

LTSP stands for 'Linux Terminal Server Project'.