Bitcoin is a form of cryptocurrency. While it's not very accessible to every day users at the moment, current projections suggest that it will be user friendly and accessible within 8-10 years. It's also important to note that Bitcoin isn't the only kind of cryptocurrency, there are 1000s. Bitcoin is just the first one that we've all agreed is going to work (by we, I mean the cryptocurrency subculture). It took 11 years of messing around before we arrived at Bitcoin, and there's no going back now.
Bitcoin revolutionizes the world in two ways.
1. Bitcoin is the first form of currency in history that A) Can't be stolen, and B) Can't be controlled. Rather than have a central banking system control the creation and dissemination of currency in order to influence the economy (often to their own benefit-- they're run by humans), Bitcoin operates on a set rate of inflation (an algorithm of "mining" that is designed to mimic the extraction of gold, with inflation and valuation being modelled after the EXACT history of gold). The system itself is impervious to attacks as no Bitcoin is actually stored on the system, but rather in your own Bitcoin wallet (plural for Bitcoin is "Bitcoin", not "Bitcoins"). Furthermore, there is a public log that is accessible to the entire world which tracks every single transaction on the Bitcoin network, though anonymously. Lastly, the whole system, including the Bitcoin, is encrypted to hell and back; unfortunately, there are still weaknesses in the wallets, which is how Bitcoin CAN be stolen from you, so the first person to invent a secure wallet will become a very rich man.
2. Bitcoin allows for global transactions in seconds with no fee, and no regulation. Suddenly anybody in the world can get a loan (more than 1 third of the world's population don't even know that banks exist), and there are plenty of Bitcoin "Banks" popping up. If we've learned one thing over the last ten thousand years, it's that money drives success, which drives development of infrastructure and society as a whole. So this is revolutionary, but it also scares a lot of people-- particularly banks and governments. It doesn't matter though; banks and governments were never going to let the internet happen, but the internet was bigger than them. Bitcoin, and cryptocurrency in general, is the same.
Last point of interest: you will probably see cryptocurrencies in the near future with fun names like GagaCoin and BeiberBucks, probably even FacebookBucks.