Definition of Hardware
Hardware refers to a physical piece of a computer. This could be a hard drive, monitor, memory chip, or CPU. The key idea is that the item is something you can touch. This compares to software which is not tangible in any way. You can't pick it up or weigh it. Yet, without software, hardware is useless.
Typical examples of hardware include the computer you're using to view this page, the hard drive that has this page stored on it, and the mouse you used to click on a link to bring you to this page.