Efficiency-cores are specialized processing units designed to handle less demanding tasks in a computer or device. They consume less power compared to traditional cores, allowing for longer battery life in laptops and smartphones. By managing background processes and lighter applications, efficiency-cores help improve overall system performance without draining resources. These cores work alongside performance-cores, which are optimized for more intensive tasks like gaming or video editing. This combination allows devices to balance power consumption and performance, ensuring that users can enjoy a smooth experience while maximizing energy efficiency.