A. Distributed File System (or Dfs) is a new tool for NT server that was not completed in time for inclusion as part of NT 4.0, but is now available for download. It basically allows Administrators to simulate a single server share environment that actually exists over several servers, basically a link to a share on another server that looks like a subdirectory of the main server.
This allows a single view for all of the shares on your network, which could then simplify your backup procedures as you would just backup the root share, and Dfs would take care of actually gathering all the information from the other servers across the network.
You do not have to have a single tree (Dfs directory structures are called trees), but rather could have a separate tree for different purposes, i.e. one for each department, but each tree could have exactly the same structure (sales, info. etc).
For more information on DFS see http://www.microsoft.com/ntserver/nts/downloads/winfeatures/NTSDistrFile/AdminGuide.asp