About custom category groups
A category group is a collection of categories. Smoothwall provide a set of standard category groups with Smoothwall Filter when you purchase it. However, you can create your own bespoke custom category groups containing custom categories that you added and categories from the standard category groups. You can then use your category group in your web filter policies, so you don't need to select so many categories when you're adding your web filter policies.
If you are a large school or organization, you might require more than one Smoothwall Filter. This means that you might have a multitenant setup. You can create custom category groups that you can use on any tenant or you can create tenant specific custom category groups. This can be useful in situations, for example, you have a lower school tenant and an upper school tenant and you want the upper school to be able to access social networking sites but you don't want the lower school to have access. Or a more complex situation where both can access Facebook but only one can access Twitter. Therefore, you would have a social networking policy for both schools, but each would be setup to their own requirements.