Bitcoin

• Bitcoin

Bitcoin is a peer-to-peer payment system introduced as open source software in 2009 by developer Satoshi Nakamoto
The digital currency created and used in the system is also called bitcoin and is alternatively referred to as a virtual currency, electronic money, or cryptocurrency

Bitcoins are created as a reward for payment processing work in which users who offer their computing power verify and record payments into a public ledger
Called mining, individuals engage in this activity in exchange for transaction fees and newly minted bitcoins
Besides mining, bitcoins can be obtained in exchange for other currencies, products, and services.
Users can buy, send, and receive bitcoins electronically for a nominal fee using wallet software on a personal computer, mobile device, or a web application.
http://en.wikipedia.org/wiki/Bitcoin

• Bitcoin

Bitcoin uses peer-to-peer technology to operate with no central authority or banks; managing transactions and the issuing of bitcoins is carried out collectively by the network.
Bitcoin is open-source; its design is public, nobody owns or controls Bitcoin and everyone can take part
https://bitcoin.org/en/

• Bitcoin network

The Bitcoin network is a peer-to-peer payment network that operates on a cryptographic protocol. Users send bitcoins, the unit of currency, by broadcasting digitally signed messages to the network using Bitcoin wallet software.
Transactions are recorded into a distributed public database known as the block chain, with consensus achieved by a proof-of-work system called "mining".
The block chain is distributed internationally using peer-to-peer filesharing technology similar to BitTorrent
The protocol was designed in 2008 and released in 2009 as open source software by "Satoshi Nakamoto", the pseudonym of the original developer or group of developers.
The network timestamps transactions by including them in blocks that form an ongoing chain called the block chain
Such blocks cannot be changed without redoing the work that was required to create each block since the modified block.    
The longest chain serves not only as proof of the sequence of events but also records that this sequence of events was verified by a majority of the Bitcoin network's computing power

Bitcoin mining
To form a distributed timestamp server as a peer-to-peer network, Bitcoin uses a proof-of-work system similar to Adam Back's Hashcash and the internet rather than newspaper or Usenet posts.
The work in this system is what is often referred to as Bitcoin mining.
The mining process involves scanning for a value that when hashed twice with SHA-256, begins with a number of zero bits. While the average work required increases exponentially with the number of leading zero bits required, a hash can always be verified by executing a single round of double SHA-256

Timestamps
The Bitcoin specification starts with the concept of a distributed timestamp server
A timestamp server works by taking a SHA256 hash function of some data and widely publishing the hash
The timestamp proves that the data must have existed at the time, in order to produce the hash
For Bitcoin, each timestamp includes the previous timestamp hash as input for its own hash
This dependency of one hash on another is what forms a chain, with each additional timestamp providing evidence that each of the previous timestamp hashes existed.

http://en.wikipedia.org/wiki/Bitcoin_mining#Bitcoin_mining

• Namecoin

Namecoin is a cryptocurrency which also acts as an alternative, decentralized DNS, which would avoid domain name censorship by making a new top level domain outside of ICANN control, and in turn, make internet censorship much more difficult, as well as reduce outages.
http://en.wikipedia.org/wiki/Namecoin

• fiat money

Fiat money is money that derives its value from government regulation or law

fiat currency
The term fiat currency is used when a fiat money is used as the main currency of the country.

The Nixon Shock of 1971 ended the convertibility of the United States dollar to gold. Since then, all reserve currencies have been fiat currencies, including the U.S. dollar and the Euro

A central bank typically introduces new money into circulation in the economy by purchasing financial assets or lending money to financial institutions
Commercial banks then multiply this base money by credit creation through fractional reserve banking, which expands the total supply of broad money (cash plus demand deposits). The amount of money in circulation is reduced by the opposite process. The value of fiat currencies is influenced by monetary policy

Fractional reserve banking
Fractional-reserve banking is the practice whereby a bank holds reserves in an amount equal to only a portion of the amount of its customers' deposits to satisfy potential demands for withdrawals. Reserves are held at the bank as currency, or as deposits reflected in the bank's accounts at the central bank.

Demand deposit
Demand deposits, bank money or scriptural money are funds held in demand deposit accounts in commercial banks.
These account balances are usually considered money and form the greater part of the narrowly defined money supply of a country

Exorbitant privilege
The term exorbitant privilege refers to the alleged benefit the United States has due to its own currency (i.e., the US dollar) being the international reserve currency.
Accordingly, the US would not face a balance of payments crisis, because it purchased imports in its own currency

Reserve currency
A reserve currency (or anchor currency) is a currency that is held in significant quantities by governments and institutions as part of their foreign exchange reserves, and that is commonly used in international transactions.
Persons who live in a country that issues a reserve currency can purchase imports and borrow across borders more cheaply than persons in other nations because they need not exchange their currency to do so.
As of 2014 the United States dollar is the world's reserve currency, and the world's need for dollars has allowed the United States government as well as Americans to borrow at lower costs, granting them an advantage in excess of $100 billion per year

hyperinflation
hyperinflation occurs when a country experiences very high and usually accelerating rates of monetary and price inflation, causing the population to minimize their holdings of money.
Hyperinflation is often associated with wars, their aftermath, sociopolitical upheavals, or other crises that make it difficult for the government to tax the population, as a sudden and sharp decrease in tax revenue coupled with a strong effort to maintain the status quo can be a direct trigger of hyperinflation.
http://en.wikipedia.org/wiki/Fiat_money