Parking a goal puts it in a permanent "on hold" state. When you park a goal, it leaves your "current" view and goes into the "parked" view.
Click on the "Parked" radio button beneath your objective guide to view your parked goals.
To un-park a goal, click "Show More" next to the goal, then click the Details tab, and click "Activate Goal". This will put the goal back into your "Current" view.