The key difference between a desktop computer and a laptop computer lies in their form factor and portability. Desktops typically consist of separate components like a tower, monitor, keyboard, and mouse, designed for operation in a fixed location. They usually offer more powerful hardware, easier customization, and better heat management. In contrast, laptops are compact, portable devices with all-in-one components, designed for mobility. While laptops have become increasingly powerful, desktops generally provide greater performance and upgrade options. Thus, the choice between them often depends on user needs related to portability and performance.