For example, clothing companies come out with new product lines and updates every year. A large amount of the "new" is due to designers creating new lengths, seems, cuts, pockets, color schemes, and the like. Designers are to products what architects are to buildings. These seem to be the creative people that challenge the limits of what is possible.
Then there are developers. Developers are to products what civil engineers are to buildings. These are the people that make it work. They apply manufacturing constraints to the designs and come up with the best solution. Their creativity is figuring out how to make something. Welded seam gloves. It's the next big thing if anyone can figure out how to do it well. Many millions of dollars if you can make gloves with welded seams that last as long as sewn seams. Companies are starting to try it now, but it is not working yet.
Right now as a do-it-all-myself person it's hard to separate the different tasks. As I apply for mainstream jobs I have some difficulty most of the time even understanding what they are looking for. In my education, proof of concept and functionality have been stressed over looks. If it worked with duct tape, we used duct tape. The more I learn about marketing it seems that people care how things look. Now, my experience in industry is very limited. So when I apply for these jobs I wonder if I will be creating new products from scratch like I have done before or if they want someone to take a prototype and make it shinny and figure out how to make tens of thousands of them.
There are many other people in the product line chain such as the people that actually manufacture the stuff, the sales people, the marketing people, management, investors/owners, and the support people that keep all of those people running. However, when it comes to the creation and production the people that create items and solve production problems are designer and developers.