Based on ONE publication, priority, or application number, you can search backward or forward citations or cited/citing patents.
A backward citation search is a typical place to start a validity search.
A forward citation search is a typical place to look for patent infringement.
A backward and forward citation search together creates a very precise subject search from the starting point of a single patent number.
Orbit automatically defaults to searching both the forward and backward citations. If only one type of citation (backward or forward) is desired, it is necessary to uncheck the unwanted citation type. The same applies if the original patent is not to be included in the search.