Bitcoin is a decentralized, digital currency used as a means to transfer value around the world. There is a lot to learn about the topic, but this explainer video is a good place to start:
Released to the public in 2008 via white paper by Satoshi Nakamoto, a pseudonymous author whose identity is still shrouded in mystery, you can read the original document here. Since then it has grown into a network of miners and users of all shapes and sizes around the world, comprising more computing power than Google several times over.
As you can see from the chart below, there is quite a bit of fluctuation in the price of bitcoin. We are long bitcoin but see opportunities and use cases for many other coins.