Bitcoin can refer to the Bitcoin network/protocol as Bitcoin (sometimes capitalized) and to the units of currency flowing in the Bitcoin network as bitcoins.
Bitcoin currency is a purely peer-to-peer version of electronic cash that allow online Payments to be sent directly from one party to another without going through a financial institution.
By design, bitcoins have several technical attributes
- Fixed supply
- Non-counterfeitable
- Divisible
- Easily transportable
Digital signatures provide part of the solution, but the main benefits are lost if a trusted third party is still required to prevent double-spending. A solution to the double-spending problem using a peer-to-peer network.
The network timestamps Bitcoin Transactions by hashing them into the Bitcoin Blockchain.
Messages are broadcast on a best effort
basis, and nodes can leave and rejoin the network at will, accepting the longest
proof-of-work chain as proof of what happened while they were gone. - bitcoin.org 
Milton Friedman talks about Internet money in 1999
How to get your head around Bitcoin?
There are many comprehensive tutorials which explain how Bitcoin works , and what it does, as well as it's role in the society, and politics.
Bitcoin Logo
One can easily learn all about Bitcoin on MOOCs and just by searching for tutorials.
However, the best way to get your head around Bitcoin is to join your local Bitcoin Meetup, though talking to people, from whom apart from technology, you can learn how to safely use, store and trade Bitcoin.
This Wiki is focused on less popularised applications of block chain technology and related concepts.