If you want to run a business and make it successful you will have to understand demand and supply. You will have to check demand and supply for the product you are selling. If demand exceeds supply, you can start selling this product, if there is less demand and high supply, it will be very difficult to profit by selling this product. When you are trying to sell completely new product, you might not see any demand. In that case, you can create demand for the product through marketing and promotion. Aggressive advertising helps you create demand for the product.