CATS gives you the ability to customize your candidate statuses as you see fit.

1) Navigate to the Settings tab within CATS.
2) Click on the Customize Workflow link on the blue bar.
3) In this case, we want to edit the candidate statuses, so click the Candidates link on the main page.

From here, you are able to:

1) Add/edit status names.
2) Add custom triggers that create tasks, emails, etc... when changing statuses.
3) Set pre-requisites for existing statuses.

When done making your changes, be sure to click the Save button at the bottom.