How does digest

[root <root @ list . cdc . gov>]

I have a list owner who wants his list to be available in digest 
format.   I added the aliases to digest the list but I don't understand
how a list subscriber would subscribe to the digested form of a list.  Is 
there any documentation available on this.  I've looked around but can't 
really find much information on the digest.  Can someone give me a few 
pointers or at least tell me what to ftp or read.

Thanks
Lee Nelson
Centers for Disease Control and Prevention
Atlanta