Selective Repeat ARQ is a data link layer protocol used in computer networks to ensure reliable data transmission. It allows the sender to send multiple frames before needing an acknowledgment for the first one. If a frame is lost or corrupted, only that specific frame is retransmitted, rather than all subsequent frames, improving efficiency. In Selective Repeat ARQ, both the sender and receiver maintain a buffer to store frames. The receiver can accept out-of-order frames and will acknowledge each one individually. This method reduces the number of retransmissions and enhances overall throughput compared to simpler protocols like Stop-and-Wait ARQ.