Related Products are any product in the same sub-category as another item. Displaying Related Products is a way to try and up-sell customers.
Getting Started:
To enable Related Products for your storefront:
Login to your Admin Area and navigate to Inventory>>Products.
In Version 5, you will click on the Purple link for Product Settings and enable "EnableRelatedProducts" and save changes.
In Winter '09, you will click Inventory>>Products and click on the Settings button. From there, enable "EnableRelatedProducts" and save changes.
There is no way to define related products. If you're looking to define related products, you can use the "ProductAccessories" field of the
Products table. The display of "Related Products" and "Product Accessories" on the "ProductDetails.asp" page is pretty much exactly
the same. You can change the title of each of these as well, to call them anything such as to say "Other products you might like..." for
example. To change the title, once again go into the Product Settings from Inventory>>Products. Here you will see the "RelatedProducts_Title" and "ProductAccessories_Title" fields.