Depending on the settings you have chosen, when a non-employee enters Chronicle, many of the tabs are hidden; the screen looks like this:
Home: Gives access to the RSS feed and a few Tools; most tools are not available to non-employees.
Email: Shows email that has been sent to the person.
Scheduler: Non-employees can only view their own calendar or employee calendars on the Scheduler tab; and they can add events but not edit events
Tasks: Non-employees can only view their own tasks. This can be relevant for subcontractors if you are using the Tasks list to communicate what needs to be done and get confirmation on what is completed.
Jobs: Shows only those jobs related to the organization the person is associated with or jobs the non-employee is associated to. The Active Jobs button refreshes the job list.
Activities: Gives access only to activities that are associated to their jobs.