Design is the creative process of transforming the problem into a solution; the solution is also called design. -- 📖 Software Engineering Theory and Practice, Shari Lawrence; Atlee, Joanne M. Pfleeger
Software design has two main aspects:
Product/external design: designing the external behavior of the product to meet the users' requirements. This is usually done by product designers with input from business analysts, user experience experts, user representatives, etc.
Implementation/internal design: designing how the product will be implemented to meet the required external behavior. This is usually done by software architects and software engineers.