Bitcoins can be accepted as a means of payment for products sold or services provided. If you have a brick and mortar store, just display a sign saying “Bitcoin Accepted Here” and many of your customers may well take you up on it; the transactions can be handled with the requisite hardware terminal or wallet address through QR codes and touch screen apps. An online business can easily accept bitcoins by just adding this payment option to the others it offers, like credit cards, PayPal, etc. Online payments will require a Bitcoin merchant tool (an external processor like Coinbase or BitPay). 
Venture capitalists, such as Peter Thiel's Founders Fund, which invested US$3 million in BitPay, do not purchase bitcoins themselves, but instead fund bitcoin infrastructure that provides payment systems to merchants, exchanges, wallet services, etc.[150] In 2012, an incubator for bitcoin-focused start-ups was founded by Adam Draper, with financing help from his father, venture capitalist Tim Draper, one of the largest bitcoin holders after winning an auction of 30,000 bitcoins,[151] at the time called "mystery buyer".[152] The company's goal is to fund 100 bitcoin businesses within 2–3 years with $10,000 to $20,000 for a 6% stake.[151] Investors also invest in bitcoin mining.[153] According to a 2015 study by Paolo Tasca, bitcoin startups raised almost $1 billion in three years (Q1 2012 – Q1 2015).[154]
To be accepted by the rest of the network, a new block must contain a so-called proof-of-work (PoW).[64] The system used is based on Adam Back's 1997 anti-spam scheme, Hashcash.[5][79] The PoW requires miners to find a number called a nonce, such that when the block content is hashed along with the nonce, the result is numerically smaller than the network's difficulty target.[3]:ch. 8 This proof is easy for any node in the network to verify, but extremely time-consuming to generate, as for a secure cryptographic hash, miners must try many different nonce values (usually the sequence of tested values is the ascending natural numbers: 0, 1, 2, 3, ...[3]:ch. 8) before meeting the difficulty target.
The unit of account of the bitcoin system is a bitcoin. Ticker symbols used to represent bitcoin are BTC[b] and XBT.[c] Its Unicode character is ₿.[72]:2 Small amounts of bitcoin used as alternative units are millibitcoin (mBTC), and satoshi (sat). Named in homage to bitcoin's creator, a satoshi is the smallest amount within bitcoin representing 0.00000001 bitcoins, one hundred millionth of a bitcoin.[2] A millibitcoin equals 0.001 bitcoins, one thousandth of a bitcoin or 100,000 satoshis.[73]

Oct. 31, 2008: Someone using the name Satoshi Nakamoto makes an announcement on The Cryptography Mailing list at "I've been working on a new electronic cash system that's fully peer-to-peer, with no trusted third party. The paper is available at" This link leads to the now-famous white paper published on entitled "Bitcoin: A Peer-to-Peer Electronic Cash System." This paper would become the Magna Carta for how Bitcoin operates today.

In June 2014 the network exceeded 100 petahash/sec.[101] On 18 June 2014, it was announced that bitcoin payment service provider BitPay would become the new sponsor of St. Petersburg Bowl under a two-year deal, renamed the Bitcoin St. Petersburg Bowl. Bitcoin was to be accepted for ticket and concession sales at the game as part of the sponsorship, and the sponsorship itself was also paid for using bitcoin.[102]

It's impossible to say how much bitcoin has increased in price single its earliest incarnation, because its value back then was in the fractions of cents. A conservative estimate, based on bitcoin's current price being around $6,300 per coin, and its early price being less than $0.01, would see bitcoin's value increasing more than 1 million fold in the last decade.
Security Risk: Bitcoin exchanges are entirely digital and, as with any virtual system, are at risk from hackers, malware and operational glitches. If a thief gains access to a Bitcoin owner's computer hard drive and steals his private encryption key, he could transfer the stolen Bitcoins to another account. (Users can prevent this only if bitcoins are stored on a computer which is not connected to the internet, or else by choosing to use a paper wallet – printing out the Bitcoin private keys and addresses, and not keeping them on a computer at all.) Hackers can also target Bitcoin exchanges, gaining access to thousands of accounts and digital wallets where bitcoins are stored. One especially notorious hacking incident took place in 2014, when Mt. Gox, a Bitcoin exchange in Japan, was forced to close down after millions of dollars worth of bitcoins were stolen.
Another interesting way (literally) to earn bitcoins is by lending them out, and being repaid in the currency. Lending can take three forms – direct lending to someone you know; through a website which facilitates peer-to-peer transactions, pairing borrowers and lenders; or depositing bitcoins in a virtual bank that offers a certain interest rate for Bitcoin accounts. Some such sites are Bitbond, BitLendingClub and BTCjam. Obviously, you should do due diligence on any third-party site.