You can control how an event/class is published online using the "Access" settings for the class.
If you don't want the class to be visible then, when creating the class, on the "Access" tab, simply select the radio button "Not visible online" for the different groups as appropriate.
If you select "Not visible online" for the "Public" group, guest visitors (i.e. public visitors) to your booking site will not see the event. But note that if you are logged in as an administrator you will see the event. If you log out as an Administrator (i.e you'll be viewing the site as a Guest/Public) you can test this and the event will no longer be visible to you.
You could also select the "Not visible online" radio button for the "Administrator" group and you won't be able to see the event on your booking site either even when logged in as an Administrator.
Remember if you want the event to be visible online you will need to change these options back to "Can view & book online" later if you want the event to be visible and bookable online.
These settings don't effect the visibility of the event in the Admin Calendar.
These options are very powerful as they let you fully control access and visibility to your classes and events. You can be working on creating and populating the content for an event in the Admin Calendar but only make it visible online when you are done. Or you can just show events but not allow them to be booked etc. If you use Jezzam's membership features and have different groups of members, you can even create events which are available to some groups but not others.