Content is currently under development for Products. When complete you will see a list of all the different documentation sections here that you can go to, inlcuding products management, attributes for products, reports, special purpose groups, reviews, modify many products at once, product feeds, modifying many image sizes at once, auto-price markups, real-time inventory, and much more. You will also be able to select these from the menu on top.
In the interim, many of the options, fields, and selection lists have context sensitive help that you can view by holding your mouse over the item.