Interchangeable parts are components that are made to be identical and can be easily replaced without custom fitting. This concept revolutionized manufacturing by allowing for mass production, where products could be assembled quickly and efficiently. It was popularized in the early 19th century by inventors like Eli Whitney, who demonstrated its use in the production of firearms. The use of interchangeable parts simplifies repairs and maintenance, as damaged components can be replaced without needing specialized tools or skills. This approach is now standard in various industries, including automotive and electronics, making products more reliable and cost-effective to produce.