Products feature is available in Advanced Pack.
Product items can be used with Opportunity and Quotes. They are also available for a customization in Entity Manager so you can create new relationships between products and other entities.
A product record has three price fields: Cost, List and Unit. There is an ability to automatically calculate Unit Price using different formulas according to a selected Pricing Type.
Products can be added as line items to a Quote record. Product fields can be printed in PDF. More detail here.
Products can be added as line items to an Opportunity record. By default this feature is disabled. You need to add 'Line Items' field to Detail layout of Opportunity via Layout Manager. Make the cell full-width wide using minus icon.
Each Product record can belong to some Product Category. Product Categories are presented as a hierarchical tree structure. Each category can have sub-categories.
Product Category is a separate entity type, hence an access can be controlled by ACL.
To be able to search products in all sub-categories you need to switch to the expanded mode in the context menu next to the root category.