Long description in rich text. Here you can write the fine details of your products. The terms and conditions, return policy for this specific product, etc.
(Group Product Example) Product Name Here
Short description of the product.
This will be closer to the picture and on the top part of your product page.
This helps search engines like google to find you better as well. So be as good at describing your product as possible. That is called SEO = Search Engine Optimization.