The Internet Control Message Protocol (ICMP) is a network layer protocol used for error messages and operational information in the Internet Protocol Suite. It helps devices communicate issues like unreachable hosts or network congestion, allowing for better management of data transmission. ICMP works alongside the Internet Protocol (IP), providing feedback about problems in the communication environment. For example, when a packet cannot reach its destination, ICMP sends a message back to the sender, indicating the issue. This protocol is essential for network diagnostics and tools like ping and traceroute, which help identify connectivity problems.