Think of this section as your chance to reduce returns if you are selling a physical product. Or complaints if you're selling something else.
This section of the Add New product form is the best spot for giving specific details (like color, texture, style, etc.) or dimensions about your service, product, etc. that might influence whether a customer is ultimately happy with their purchase.
Imagine thinking you ordered the item on the left and ending up with the item on the right? The description space gives you the freedom to add any images and copy you need to help make sure your customer is clear about what they are purchasing.
It also gives you a chance to make some common sense suggestions to them so they can ensure they are buying something they will be happy with. Like "don't forget to measure the space you have available." Or "please check our clothes sizing chart before buying." 'Or this item comes in multiple colors, please double-check the color you are ordering."
It's always a great idea to also include these dimensions and reminders in images as well that you add your your image gallery - again to make sure the potential customer sees them and reduces the chance of purchasing something that isn't right fit for them, their space, or their personality.