User types are governed by the level of access granted to them. The different access level 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