Idle user means that there wasn't an authentication success record for 1~6 months. 

If you're curious what this feature does, please refer to the New Feature Guide of 2.2.x at our knowledgebase: BioStar 2 Features

One of the hurdles in access control system management is to find an effective way to manage information of users such as temporary or resigned employees and those who were assigned temporary entrance rights.

To make this task more manageable, the long-term idle user management feature was added to allow the administrator to see idle users for a specific period (1~6 months) in a single glance, and to modify and delete user information.