The function epoll_ctl is part of the epoll interface in Linux, which is used for monitoring multiple file descriptors to see if they are ready for I/O operations. It allows applications to efficiently manage a large number of connections, making it suitable for high-performance network servers. epoll_ctl can add, modify, or remove file descriptors from an epoll instance. It takes parameters such as the epoll file descriptor, the operation to perform (add, modify, or delete), and the target file descriptor. This flexibility helps developers optimize resource usage and improve application responsiveness.