When you register for a new Rossum account, both Organization and User accounts are created.
You can view an Organization as a container for all the workspaces, queues and documents that you can see when you log in to your Rossum account. The Organization name is usually the same as your company name you filled during the registration process.

Organization and username
Moreover, one Organization can serve as a workplace for multiple Users. The User who created the trial account of the Organization is an Admin User. The User can now create and edit other User accounts and assign them rights to Queues as needed.

User Settings in Rossum
The best practice when you have already created an Organization account for your company is to create new user accounts for your colleagues directly via the users settings. After being invited, your colleagues do not need to go through the whole trial registration process.
Please note that users cannot be moved between different Organizations. If you already created a new Organization account and you would like to share the same Organization account with a colleague of yours who had created a different Organization, go ahead and create a new user account for your colleague via the users settings instead.