Wire size refers to the thickness of electrical wire, which is crucial for safely conducting electricity. It is typically measured using the American Wire Gauge (AWG) system, where a smaller gauge number indicates a thicker wire. Thicker wires can carry more current without overheating, making them suitable for high-power applications. Choosing the correct wire size is essential for preventing electrical hazards, such as short circuits or fires. Factors like the length of the wire run, the amount of current needed, and the type of insulation also influence the appropriate wire size for a specific project or installation.