A frevvo' user is anyone that is authenticated to  for to frevvo for the purpose of:

• Designing a form
• Digitally signing the form ( needs frevvo needs to know who the user is in order to generate a signature)
• Participating in a workflow ( needs frevvo needs to know who the user is in order to display a task list)
• Submitting a form that requires authentication to access
• Access the audit trail (identifying the submitter, for example) and part of the audit trail history
• Using an external security manager (LDAP/Active Directory, for example) with Single Sign On (SSO)

Anonymous Users

These are users that don't need an account in frevvo and also aren't involved in any of the items described above. Anonymous users do NOT count as frevvo users and therefore are not limited by the license. Common examples are filling out a survey or a contact form.

Concurrent Users

Concurrent users are frevvo users that are logged in to frevvo simultaneously.
Generally, for Intranet forms/workflows you want to calculate how many users will concurrently be accessing the forms, since in most cases, on an Intranet, people want to know who is submitting the form. For Extranet forms, you generally do not have authenticated users. For instance, a 10-concurrent user license means 10 users can be logged in simultaneously to frevvo.