What are the account types of 'External User' and 'Service' used for?

There are three security profiles available:

• Admin - assigned to users who have administrative privileges within the application including managing configurations, users and groups, etc.
• CMAdmin - assigned to users with limited administrative privileges within the application including admin approvals, etc.
• User - assigned to users with general access within the application including creating and editing proposals, submitting proposals for review, etc.

You can see more details on the default permissions that are associated with each role here.

The External User and Service option are not used within CM - they have no additional function and contain the same settings as  'user.' These additional types of accounts may be used when you have more than one Kuali product, but do not have any function within CM.