You can restrict visibility of products by user department. To deny visibility to a particular department, select its name from the ALLOWED list and click the deny button. To allow visibility, select the department name from the DENIED list and click the allow button.

This restriction affects anything that can be associated with a product, which includes tasks and faqs. So if you deny a product to a particular department, then no one in that department will see any task or faq relating to that product.