To configure a product you need to select a type for it.
Choosing a type for your product will help you configurating the recipe and you will need to choose from the following options:
I sell it as I buy it - means that your product will be sold exactly as you bought it and will contain only one stock.
Below you can find more information about what a stock is:
Contains recipe - this means that the product you are configuring contains multiple ingredients ( contains raw materials) and enters a production process, this way you will be able to add in your recipe only raw materials.
More information on raw materials:
Service - this means that the product doesn't contain a stock or raw materials so you won't be able to add any in the recipe.