You've opened the IDE Sandbox, an environment that you can access on "readme" and "code-along" lessons in Learn. It's a great place to experiment with code!
Saving varies by the type of work you are doing:
-- Most of the work you do in the Sandbox is automatically saved on your behalf to the
learn-co-sandbox repository in your GitHub account. Please DO NOT touch this repository in GitHub. Doing so will affect your Sandbox experience, and potentially cause your work to fall out of sync.
-- Git repositories that you clone into the Sandbox are NOT automatically saved. In this case, you are responsible for committing and pushing your work to GitHub.
To learn more about the Sandbox, please visit http://help.learn.co/technical-support/learn-ide-in-browser/ide-in-browser-sandbox