IPv6 is the next generation Internet Protocol. That is, basically, the addressing system computers and routers and such use to direct traffic around a local network, and the internet. IPv4, the last version, was thought up in the world that existed when PCs didn’t exist, really, and no one could even imagine that, well, you’d want to give your refrigerator an IP address. It allowed for 4,294,967,296 addresses. Which, on one hand, seems like a lot, but it’s not, when every cell phone, PC, router, cable set top box and toaster has one.

So in comes IPv6, a different kind of addressing protocol. It allows for 5×10²⁸
addresses, which, for those interested, is 50 octillion. It will likely even manage to make it into space, I think.

One of my favorite people who makes geeky stuff understandable is Carla Schroeder. She wrote a great series of articles for O’Reilly about IPv6. They are worth a read.