Form factors refer to the physical size, shape, and layout of electronic devices and components. They determine how devices fit into systems and interact with other hardware. Common examples include the ATX motherboard size for desktop computers and the mini-ITX for smaller builds. In addition to motherboards, form factors apply to various components like hard drives, power supplies, and cases. Each form factor has specific dimensions and mounting points, ensuring compatibility within a system. Understanding form factors is essential for building or upgrading computers, as it affects performance and space utilization.