There are 4 plan statuses:
The status automatically progresses as described above. But you can manually change it too.
You can change the status by opening a plan, clicking Manage plan on the main plan page, and then selecting Change status.
There's also options on the plan list to change the status:

Click the flag icon next to the plan you want to change.
Tip: You can also do this in bulk by selecting multiple plans and using the Change status bulk action.