It's understanding the users and their needs and deciding on the features that will meet those needs. A design specification includes a complete description of the product's appearance and behavior. It may include a working prototype to illustrate the design. Usability testing . By observing real users interacting with your product, we locate problems and identify strengths.
Usability testing gives valuable feedback at any point in the development process.
Better to test during development than find big problems after you ship. Expert product review. We can do an expert review of existing products without bringing in any users. A review contains observations based on good design practices and knowledge of your customers. It's faster than a full usability study.