Hello Luc,

1: product.template (Products Menu)

    Actually it is not a product it is Product template

     whenever you are creating Product (product.template) than same will be created in also (product.product)
    it contains the main product and with list of product variant (attributes)

 2: product.product (Product Variants)

     Here there are actual products with their variants as a separate products

    When ever you are creating SO or PO than actually you are using Product variants not Products

3: Product Attributes
     

     To create Product Variant you need add Product Attributes to that product which will automatically Create Product Variants 

     Example:

         there is an Product Named (Moto G)

         so by default it will be in product.template and product.product

         Now, if you want to add Variant than you need to create Attribute and add to that particular

         Imagine You have created Memory as an attribute and 16 GB and 32 GB as that attribute value

         than it will be total two Product in Product Variants

     You can Create Attribute From Product Categories & Attributes --> Attributes

     You can Create Attribute Values From Product Categories & Attributes --> Attribute Values


Thanks