1) The supplier workspace allows you to configure the following:
a) approval workflow for new supplier organizations that are created
b) approval workflow for profile updates done by suppliers
c) approval workflow for profile updates done by internal users
d) frequency to notify suppliers to update their profile
e) timeframe when certificate expiration reminders should go out
All these are setup within the tasks in the workspace and get triggered based on SPQ changes.
2) If you have an integrated suite realm the common supplier is shared between the two and contracts for contract compliance.