The green bar at the very top shows your Save button, as well as two other options.
Here is a guide to what they are:
Where it says 'Blocklab >' Then the page name, these are called Breadcrumbs. By clicking on Blocklab, it will take you back to the Blocklab selection page rather than going back through your account.
A link that opens a new tab to your website. This will show how your website looks on the live page.
Ever had it where you changed an entire layout, saved & published, then wanted to revert back to the last one? This is where Versions comes in handy. Similar to undo and redo, pressing the left or right arrow can guide you back and forth to designs you have created. The fast forward button will take you to your most recently saved/published design.
The publish button is self-explanatory, it will publish the design you created to your website.
However, have you noticed this happens to any changes you make?
This means any changes you make are automatically saved on Blocklab, but will not be published until you press 'Publish'.