Understanding motherboard form factors is crucial when purchasing a new motherboard because it determines compatibility with the computer case and influences the overall system configuration. Motherboard form factors dictate the physical dimensions, layout, and placement of components on the motherboard. Different form factors, such as ATX, MicroATX, and Mini-ITX, cater to diverse system sizes and usage scenarios. Selecting the appropriate form factor ensures that the motherboard fits correctly into the computer case, aligning screw holes, ports, and connectors. Additionally, form factors influence the number of expansion slots, RAM slots, and other features available on the motherboard. A mismatch between the motherboard form factor and the case can lead to installation challenges, limited upgrade options, or the need for additional components. Therefore, having a clear understanding of motherboard form factors is essential for building a compatible and well-configured system.