IP stands for "Internet Protocol", a worldwide standard that allows for computers on the Internet to talk to each other. IPv4 is the 4th version of that protocol, and although it has been extremely successful - we've all been using it, usually without thinking about it - it still has some limitations. Most urgently, as more and more devices are added to the Internet, public IP addresses - a number given to every device accessible on the public Internet - are running out. This is called "address exhaustion". Nobody is really sure when Internet addresses will be completely depleted. Estimates vary, but it will probably happen in this decade.
"Address exhuastion" also happens in other systems. Think about the phone system. Phone numbers used to have 4 or 5 digits. As more and more subscribers were added, available numbers were soon depleted and phone companies were quick to add more digits to phone numbers. So now you can see phone numbers with 6, 7 and even 10 digits.
Unfortunately, with the Internet it's not as simple as adding a few more digits. That's where IPv6 - the next version - comes in. It takes care of the depletion of IP addresses. At some point - again, nobody's really sure when - IPv6 will take off and start being used more widely.
If you're interested in learning more about IPv6, DrukNet has recently posted a free training offer, with the following disclaimer:
However, we would like to inform you that we are no experts in IPv6, but would like to share what little we know and are willing to learn from you too.More information about DrukNet's vision for an "IPv6-ready country"" is available here.