Shared mailboxes provide a means to receive email at a general (rather than personal) address. Mail is delievered to a centralized location where it can be accessed by up to ten people.
Google Groups provide a means to receive email at a general (rather than personal) address. Email sent to the address is redirected to one or more individuals at their personal addresses, and not held in a central mailbox. Google Groups can also be used to assign permissions within Google, such as the ability to view a Google Calendar, Document, or Site.
Listservs allow the creation of and subscription to email lists. These lists are configurable by the list owners and are used to distribute mail among subscribers.
For a similar service using GoogleApps@Brown, see Google Groups.