In your calendar view, there are both "published" and "unpublished" categories for your assignments. While the unpublished view is beneficial if you want to delay displaying an assignment, you can also use it to not display an assignment at all. Many teachers have grades that do not involve action from the student such as participation, preparation for class, or lab skills. These can be added to the calendar as unpublished and with an attached gradebook event, you can still grade the assignment but the students don't need to be alerted to it.
In order to create these events, create an unpublished event with an attached gradebook assignment, and a point value. Participation grades can be added in Gradebook and saved, but students and parents will not be able to see these grades.
This is a great way for you to enter grades for students on things that they may not have to produce a final product for. As mentioned in the video, the gradebook events that are not visible on the calendar can still be seen if your gradebook is visible to parents and students!