Anybody can take the quiz, but only paid subscribers can create quizes.
By selecting this option, you will create a puzzle that other people can solve online, and when done, send you the results via email. I.e., you are the teacher, and you have a number of students that will be answering the quiz.
This leaves you what to do with the results.
This mode turns off the answer keys, otherwise cheating is way too easy. It also turns off the button to check the answers online. However, there are many ways to cheat so don't assign undue weight the results of the quiz that you receive this way.
If you choose to list the puzzle for the public, you may get email from unexpected people. If you don't list the puzzle for the public, you can still send the puzzle URL to the group via email or other means.
This is a restricted option. If this was free, then a bad actor could create a "quiz" and say they were "firstname.lastname@example.org". Then they could answer the quiz and fill in the comments so that the spam target received the spam. We don't want that to happen.