Computer hardware refers to the physical components of a computer that can be seen and touched. These components include the case, central processing unit (CPU), random access memory (RAM), monitor, mouse, keyboard, computer data storage, graphics card, sound card, speakers, and motherboard. Hardware is different from software, which consists of written, machine-readable instructions or programs that tell physical components what to do and when to execute the instructions.

Hardware can be categorized as either internal or external components. Internal components are necessary for the proper functioning of the computer, while external components are attached to the computer to add or enhance functionality. Examples of internal components include the CPU, RAM, and hard drives, while examples of external components include monitors, keyboards, printers, and scanners.

Hardware and software are complementary, and a computing device can function efficiently and produce useful output only when both hardware and software work together appropriately. When using computer hardware, an upgrade means adding new or additional hardware to a computer that improves its performance, increases its capacity, or adds new features.

In summary, computer hardware refers to the physical components of a computer that can be seen and touched, including internal and external components. Hardware and software are complementary and work together to make a computing device function efficiently.