It seems that this week will see the end of the line for the allocation of IPv4 addresses (those 18.104.22.168 digits to which every www address is mapped). In others words, the internet is full.
Thankfully, a new version, called IPv6 was introduced in 1995, but still remains far from mainstream. This introduced additional digits (actually doubling the number of digits brings an exponential return in terms of the number of allocations available), but has to be supported by all the devices on the internet if it is to work properly. Also, typing (and remembering) 24 digits is a bit of a pain...
This may all seem somewhat esoteric in the bigger scheme of things, but this building block is fundamental to the internet, and everything that we do using the internet will fall over if it does not work.
So, the next time you buy any kit or specify any service, make sure it's IPv6 ready!