There are two levels to CLASS accounts that need to be understood when working with CLASS accounts; Worker Accounts (red box below) and User Accounts (green box).
A Worker in CLASS is a record of someone who has existed at some point, usually an existing or past lawyer or volunteer or someone who has at some point created or been assigned to a client or service record. Workers turn up in Conflict check, and because of this some centres are adding all kinds of people related to the centre, but not necessarily active staff. Examples include board members, contractors, IT support etc. They do this to indicate any potential conflicts.
A User Account is a sub-set of the above Workers. These are only required if a worker requires log-in access to CLASS. A user account may be active or inactive, and only currently Active User Accounts can access the database. Users accounts are where Administrators set up Permissions (via Roles).
Detailed documentation on creating and managing workers and users accounts can be found here: Creating and Managing Worker and User Accounts
Mutli-factor authentication update: note post December 2021 CLASS now authenticates with your organisations Microsoft accounts through a federated authentication more details here