Bitcoin is decentralized and it is completely peer-to-peer. What this means is that it there is no central server running the network. Each computer on the network is called a node and on equal footing with all the others. I am simplifying for the sake of this post, but the general idea is that even if you were to shut off many of the computers on the network, the network would continue to operate. Also, since the network is just a series of connected computers, there is no central place to manipulate the network. This means governments have no means to stop it. They cannot freeze accounts or funds, and there is no server that a hacker can break into to get all the money out of the network.

Of all the videos about Bitcoin, this one is the most simple and informative. Keep in mind that some of what it says is over simplified in order to get the point across, but it serves as a good starting place. (I also don't agree that is the best place to get a Bitcoin wallet even though the video says that is the case). None the less, a great short video introduction to Bitcoin that talks about the decentralized peer to peer aspect.