You get to view all your submitted applications on this tab and it shows you where you're at in the process for each position you've applied for.
There are six stages to your application journey:
1/6: Pre-Screen Questions
2/6: Video Q&A
3/6: Portfolio & References
4/6: Online Interview
5/6: Background Check
6/6: Offer & Placement
Once a company progresses you to the next stage, you'll get notified by email and given guidance on the next move that you need to make.
Depending on the status of the hiring process, you may have an action to perform. 
When the status button (the button underneath the 'Action' column) is greyed out, it means there's no action required from your end at that time. Keep an eye on this button and the "Action" column!
Both your progress and the feedback on your application depend on the company you're applying to work for and their own recruitment flow. Pay attention! They will advise you on the next steps in the process.