a subscriber is a voice mail only user - they can get their voice messages and faxes over the phone or over the seperately licensed web based in box. The Unified Messaging subscriber is allowed to get their messages from over the phone as well as from a desktop client (Outlook) and use the Outlook VMO plug in and TTS their email over the phone.
There's a feature to get at your voice mail messages and faxes via a web inbox via the Cisco Unity Personal Assistant - this is licensed seperately. You can read more about it in the user guide here:
There's a section in there on checking messages that includes a discussion of the web based inbox.
Fax is supported for both VM and UM licenses. You can use a number of 3rd party fax servers that integrate with Exchange or you can use the IP Fax functionality in 4.0(4) - you can read more about that on the IP fax server page:
