If you have ever been asked to get your IP address for any reason, you might have had occasion to hit ipconfig or something of the sort, and come up with something like 1.2.3.4 -- or even 1.02.123.4.
And this has been written in what's called IPv4. But apparently the global set of IP addresses is about to run out. Soon.
How soon?
Either this year, or next.
It's going to be replaced by IPv6. IPv6 will have a 128-bit address versus a 32-bit address (This means longer addresses, more like 1234.5678.9012.3456 or the like). Address reassignment will be faster when you change Internet providers. There should be more and better network security. Router processing will be simplified (which I suspect will mean faster data transfer -- e. g. quicker downloads and uploads).
The current system has about 4 billion addresses. The new one will have available about 340 undecillion (yes, that's a real number; it's 10 to the 38th power), or 5 x 10 to the 28th (e. g. an octillion) for all of the 6.8 billion people alive today.
Oh and backward compatibility is not great. So there is going to be some scrambling in the next few months, to get the translation programs up to snuff. It will be quite an opportunity for anyone who wants to learn IPv6 programming -- I suspect those people will be able to write their own tickets.
For more information, see:
http://en.wikipedia.org/wiki/IPv6 and
http://ipv6.com/