Client-server interaction?

[Applix747]

Is there a description somewhere of what actions CVS exeutes on the
server
and client for various commands?

E.g., for the "update" command, how does CVS decide which client files
differ from server files?  Does it require client-server traffic for
each file?

E.g., when updating a client file, what does CVS do?  Does it resolve a
series
of "diffs" on a base file stored in the server?  Is this slow if the
client
file is many revisions out of date?