Bitcoin

Bitcoin is a cryptocurrency and worldwide payment System. It is the first decentralised digital currency, as the system works without a Central Bank or single administrator.The network is  peer to peer and transactions take place between users directly through the use of cryptography, without an intermediary.These transactions are verified by network nodes and recorded in an immutable public distributed ledgers called a block Chain. 
Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies,products, and services. The word bitcoin first occurred and was defined in the White PAPER that was published on 31 October 2008.It is a compound of the words bit and coin.
Small amounts of bitcoin used as alternative units are millibitcoin (mBTC)and satoshi. Named in homage to bitcoin's creator, a satoshi.
A millibitcoin equals 0.001 bitcoin, one thousandth of a bitcoin or 100,000 satoshis.