User types are governed by the level of access granted to them. The different access levels in Freshping are:

Owner -  The account owner is the highest level of access. There can be only one owner per account. Owners can create, edit, and delete checks; they can add users, remove them and change their access levels. Owners can also transfer ownership to other admins. 

Admin - Have the same access level as the owner barring the ability to remove the owner from the account. 

Read-only - These users can log in to the account, but can only view the checks assigned to them.

Contact - These users can only receive alerts.

Learn how to add users here