The "Long Run" in economics refers to a period in which all factors of production and costs are variable. Unlike the short run, where some inputs are fixed, businesses can adjust all resources, including labor and capital, to optimize production. This flexibility allows firms to achieve economies of scale and improve efficiency over time. In the long run, firms can enter or exit the market freely, leading to a balance in supply and demand. This concept is crucial for understanding how industries evolve and how competitive markets reach equilibrium, impacting prices and resource allocation in the economy.