Plus+ members, Professor Plus+ members and their students may select the privacy settings per sketch when they create a new sketch, and update these settings at any time by clicking (i) and Edit button. 

"Who can see your sketch" dictates which users have access to view your sketch. 

"Who can see the code" dictates which users have access to view your code. (Keep in mind, savvy users may be able to use browser developer tools to view your code anyway ;) 

Professor Plus+ members can also change their Class privacy settings by editing their Class and selecting "On" or "Off" under the Private setting. 

This dictates whether the public will be able to see sketches submitted to your class, the students in your class, or the syllabus/class page.