Refresh System Tree is a choice from the Tools menu. The purpose of this is to reinitialize PBSearch without having to exit and come back in.
It clears all object source and directory information from memory and rebuilds the System Tree.
Refresh Directory is a choice from the Tools menu and has a shortcut of Ctrl-R. The purpose of this is to clear all object source and directory information from memory and reload the directory.
If PBSearch has been running for a long time and you know that many objects have changed, it would be a good idea to do one of these types of refresh.