Every business has products of some kind because a product could be anything from widgets to motel rooms. It could be something physical that you buy to resell or physical such as your labour cost but a product could also be something virtual that you rent out for a time.
As a general rule, if you sell it or hire it then it is considered a product. Sometimes a service is also a product, for instance a mechanic who fixes your car does a service, which is a product. Her or his labour is the product.
When it comes to adding products to your web site there are two options. You can simply promote and support your product using your page to describe the product, extol the benefits and supply instructions for using it.
You can also sell your product directly off your web site.
To sell products via your web site you will need an extra plugin called WooCommerce and this allows you to sell your products directly from your website. People order goods directly from your website, pay you via Paypal and you ship or supply what you promised.
The other type of product is the display only product where you display your product, describe your product, provide support for your product in the way of user manuals or flyers. For example the wood stove,