The Contacts tab displays the Contacts held for that client in Xero Practice Manager.
If you have Include Client's Contacts set "On" in your practices AutoFile settings, AutoFile searches the Client's Contacts to find a match for the Client Name. If an email is sent or received from the email address of one of the Contacts that is held for a client in Xero Practice Manager, this will match on the client when an email is autofiled. This allows emails to be filed to the client when they are send or received to/from internal team members, bookkeepers, advisers, etc. Refer to Email AutoFile Settings and Exclusions.