Bitcoin is a cryptocurrency and a payment system, first proposed by an anonymous person or group of people under the name Satoshi Nakamoto in 2008. Bitcoin is decentralized, meaning it is not subject to government or financial institution control. The system is peer-to-peer, and transactions take place between users directly, without an intermediary.
These transactions are verified by network nodes through the use of cryptography and recorded in a public dispersed ledger called a blockchain. Bitcoin is unique in that there are a finite number of them: 21 million.
Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services.
As of February 2015, over 100,000 merchants and vendors accepted bitcoin as payment. Bitcoin can also be held as an investment.
The price of a bitcoin fluctuates constantly and is determined by supply and demand. When demand for bitcoins increases, the price increases, and when demand falls, the price falls.
There is no guaranteed minimum or maximum price.
A single bitcoin is divisible down to eight decimal places (0.00000001 BTC), and can be further divided if necessary.
This allows for very fine granularity of transactions (each BTC can be divided into 100,000,000 units).
The total supply of bitcoins that will ever be created is 21 million. This number cannot be changed and the rate at which new bitcoins are created cannot be changed without changing the code that governs how bitcoins are created (the software that runs the bitcoin network).
The code governing how bitcoins are created is open source and available for anyone to review or modify.
The number of bitcoins in existence grows every day as more bitcoins are mined or created through other means such as trading or purchasing them on exchanges. The total supply of bitcoins will eventually approach 21 million but will never exceed it.
This is because the code that governs how new bitcoins are created has a finite limit: once 21 million have been created no more can ever be created.
Bitcoins are mined using specialized computers and software designed to solve complex mathematical problems; miners verify and record these transactions in the blockchain public ledger to receive their reward of newly minted Bitcoins and transaction fees paid by the senders of each transaction verified. The mining process requires substantial computing power and electricity consumption so it is typically done by large organizations with access to cheap electricity and specialized hardware such as ASIC chips designed specifically for mining Bitcoin.
Miners who verify transactions earn these rewards as well as transaction fees paid by senders of each transaction they confirm; these rewards incentivize miners to keep verifying transactions despite the costs incurred in doing so.
The current block reward for miners is 12.5 BTC per block mined which will result in an eventual total supply of 21 million BTC; this number was chosen deliberately so that there would never be more than 21 million BTC in existence and therefore no need for fractional units such as “bits” or “satoshis” (smallest unit of account on the Bitcoin network).
Note that because blocks are mined on average every 10 minutes but the time between blocks can vary significantly miners typically receive their rewards plus transaction fees paid by senders with each block they mine; currently miners receive around $600 worth of BTC per block mined on average but this value fluctuates depending on the current market value of BTC as well as the total number and size of transactions included in each block mined (larger blocks mean more fees earned per block).
To summarize, there will only ever be 21 million BTC in existence; this number cannot be changed without changing the code governing how Bitcoin works. Currently, miners earn 12.5 BTC plus transaction fees paid by senders with each block they mine; this provides an incentive for miners to keep verifying transactions despite the costs associated with doing so.