Sub-Statuses are a great way to see exactly what stage your candidates are at in the application pipelines. From the example below we can clearly see these candidates are in the 2nd-interview stage of the pipeline - and with Sub-Statuses we can further drill down to see an additional level of status.

To configure these, your Admin users can head to Settings > Admin Settings > 1. Organizational Settings and then scroll along to Sub-status. 

These are easily configurable allowing you to tailor them specifically for your companies needs and business processes. These can be anything you want!

Sub-status can also be shown in the Livelist. To setup, simply go to Livelist settings and enable the column for sub-status.