The 'User Is In Any Users' will verify that the current user is one of the selected users.
You must specify the allowed users when configuring the check. For example:
For information on how to configure a condition for a workflow transition in Jira, see the Jira documentation.
A workflow is configured so that the 'Automation' transition has the 'User Is In Any User' check = 'jsu-technical-user' user only. This is a user account that does not belong to an actual person but is used for all kinds of automations. It has more permissions than normal users, so automations can do things that would be restricted for normal users.
A normal user viewing an issue in that workflow will not see the 'Automation' transition.
This is a perfect use-case to hide a Transition that will be triggered by a 'perform as user' (impersonate) Post-Function. So you configure also 'jsu-technical-user' as the 'perform as user' in the Post-Function.
Only the manager
You might restrict some transitions in your workflow to a manager or deputy.