Content created on your site (products, categories, content), can be set to be visible or invisible. This allows you to preemptively create content and make it visible when you're ready.
You can also mark content as invisible as an alternative to deleting it; this allows you to create seasonal content and leave it for next year.
There are check boxes to control the visibility of these content pieces:
Product:
Category:
Widget:
Note: Visibility on categories affects products within the category; if the category is invisible, products inside the category are also going to be invisible (if they are not visible in other categories) and excluded from search results. This will also affect sub-categories and products in those sub-categories.