There may be a number of reasons why you may want to hide a category from the store front, this is easily done through the admin.
Products > Categories
Select the status of the category...
Active - The pages are live and on the menus and site structure
Disabled - This denies ant access the the category page
Hidden - The pages are live but do not show up to users on the store front
All these settings still allow store admin to work with the category page and add products still.