What is "playground mode" in Google's Colaboratory? : <p>I recently discovered Colaboratory. After playing with it for a few minutes, I have some idea what "playground mode" is - that no output is saved in that mode, but couldn't find a formal note in the FAQ or other help material (intro notebook) that I located. I'm wondering if there are more details to know about this mode and when is it suggested to be used?</p>

<p>Thanks.</p>
