Product design is an important part of developing your idea into a viable, marketable product. It is the process of considering the product function, appearance and how it will be done.
An inventor can do this himself but a number of professional product designers may need to be employed. Product design can also help to answer two important questions:
Is my idea technically possible?
A product designer can conduct a feasibility assessment of ideas to ensure that your product will work and is likely to produce. Some simple products may not require this step, but for others, it is important to ensure time is not wasted to visualize or prototype an idea that is not viable. If you want to learn product designing, then you can join best design sprint training.
Can anyone buy my idea?
Who better to answer this question from a buyer for a major retailer, manufacturer or distributor of market sectors is right for your product? They are the people who deal in the right market and they know it best.
In order to effectively present your ideas to the industry experts, it would be prudent to properly design and professionally present your ideas.
A good product designer needs a 'back of an envelope sketch' and turn it into thought through, a concept was developed that will impress and help get useful feedback from the industry.