Registered person is User or Contact depending on the type of goals they want to achieve while using application; Contacts are support seekers, and Users are support givers. Contacts are grouped in Accounts and Users in Teams.

User can be additionaly called Support representative, Manager, Administrator, etc. depending on the Role (assigned privileges that determine the type of access they have to the help desk application) his Team is in. When we are talking about User Types, we are talking about your support representatives, administrators, support managers, etc.