All Class Central profiles are private when created, but you can make yours public so others can see your profile, the courses you have finished and are working on, and all the reviews you have written.
To choose between Private and Public, go to Account Settings. Check or un-check the box under Public Profile, then select the blue Save Profile button at the bottom of the page.
Reviews you have added while signed in to your Class Central account display your username and profile picture. Reviews added when not signed in are marked Anonymous.