Products and services can have what is called a “variant”. For example we can ask for a financial service on 6, 12 or 18 months. Those can be considered as a variation of the service.
Products can also have variations. For example a shirt can be bought in many different sizes. In such a case we will have a single variant. But it is not the only variation of a shirt, we can have many different colours of the same shirt, so we will have two variations of the same product. We can also have the logo on it which might change...
So many products might in fact be the same at the origin and must be represented with a unique document within the IT system. Otherwise it is not possible to manage your products or services correctly.
How are products differentiated from one to another is up to the company. One company will think that a shirt in a different colour is a different product, one will think that it is not different. There is no universal way to categorise the products and it will always be made according to the point of view of the company.
The goods which are sold must be linked with a selling price. As we just have seen that a single product can have many different variations, the final price may not be the same. For example with clothes, if they are bigger, we might want to sell them a little bit more. So each variation can change the global price.
The other source of price variations is the quantity which is bought. The more we buy, the less they cost. So we must be able to create matrices with price and quantity for each of our products.