The "Save" button appears when you are editing a document. It becomes active after you made a change to your document. If you did not make any changes it will say "Saved".
Clicking the "Save" button will save your document and make your changes visible to visitors of your website. It will also close the edit bar, which causes you to see the document just like any visitor of your site would see it.
There is no need to hit the page button every minute, since a draft of your document is always saved automatically in the background. If you close your browser screen and return to the page, you will still have your draft.
If you want to save you page without closing the edit bar, you can use the keyboard shortcut: Control-S on Windows/Linux or Command-S on Mac.