Xnest is a nested X server that simply relays all its requests to another X server, where it runs as a client. This means that it appears as another window in your current X session. Xnest relies upon its parent X server for font services.
Use of the Xephyr X server instead of Xnest is recommended.
More information about X.Org can be found at:
This package is built from the X.org xserver module.