You have selected buying (in reference to you as the user) and now you need to select if you are buying a product or a service. This site goes beyond the other price comparison sites that only allow you to get comparisons of stocked consumer products. This site also goes farther to allow buying or selling of products or services that are stocked items or to your selected options.
This is the correct selection if you are seeking of getting a Product or Service.
If you have something to sell then you should select Selling tab above. This is not an eBay like site where you can list stock items where people bid on them. It allows business to automate the time consuming task of pricing when options are involved.