'IPv6' refers to the Internet Protocol version 6, a protocol for routing internet traffic. It is designed to replace the older IPv4 protocol, primarily because of the exhaustion of available IPv4 addresses. IPv6 features a vastly larger address space, allowing for a practically unlimited number of unique IP addresses. Additionally, it improves aspects of network efficiency and security through features like simplified packet headers and built-in IPsec for encryption and security. IPv6 is crucial for the future of the internet as devices become more interconnected.