Bitcoin is a digital and global money system (currency). It allows for the pseudo-anonymous (not linked to a real name) trading of money across the internet. The mathematical field of cryptography is the basis for its security.
|฿ or Ƀ, disputed.
|BTC, Coins, XBT
One of the differences between using bitcoin and using regular money online is that bitcoin can be used without having to link any sort of real-world identity to it. Unless someone chooses to link their name to a bitcoin address, it is hard to tell who owns the address. Bitcoin does not keep track of users; it keeps track of addresses where the money is. Each address has two important pieces of cryptographic information, or keys: a public one and a private one. The public key, which is what the "bitcoin address" is created from, is similar to an email address; anyone can look it up and send bitcoins to it. The private address, or private key, is similar to an email password; only with it can the owner send bitcoins from it. Because of this, it is very important that this private key is kept secret. To send bitcoins from an address, you prove to the network that you own the private key that corresponds to the address, without revealing the private key. This is done with a branch of mathematics known as public key cryptography.
A public key is what determines the ownership of bitcoins, and is very similar to an ID number. If someone wanted to send you bitcoins, all you would need to do is supply them your bitcoin address, which is a version of your public key that is easier to read and type. For example, if Bob has 1 bitcoin at the bitcoin address "ABC123," and Alice has no bitcoins at the bitcoin address "DEF456," Bob can send 0.5 bitcoins to "DEF456." As soon as the transaction is processed, Alice and Bob both have 0.5 bitcoins. Anyone using the system can see how much money "ABC123" has and how much money "DEF456" has, but they cannot tell anything about who owns the address.
In the example above, "ABC123" and "DEF456" are the bitcoin addresses of Bob and Alice. But Bob and Alice both have a second key which only they know. This is the private key, and it is the "other half" of a Bitcoin address. The private key is never shared, and allows the owner of the bitcoins to control them. However, if the private key is not kept secret, then anyone who sees it can also control and take the bitcoins there. This happened on live TV when Bloomberg's Matt Miller accidentally showed a private key to viewers. The money was taken immediately. The person who took it, told others about it later, saying "I'll send it back once Matt gives me a new address, since someone else can sweep [empty] out the old one."
Sites or users using the Bitcoin system are required to use a global database called the blockchain. The blockchain is a record of all transactions that have taken place in the Bitcoin network. It also keeps track of new bitcoins as they are generated. With these two facts, the blockchain is able to keep track of who has how much money at all times.
To generate a bitcoin, computers run specialized software. Because of how complicated the math needed to generate a bitcoin is, they must be calculated with very powerful processors. These processors can be found in CPUs, graphics cards, or specialized machines called ASICs. The process of generating the bitcoins is called mining. People who use their computers to mine Bitcoin, are paid with a small percentage of the bitcoins they generate.
A popular image associated with Bitcoin is a QR code. QR codes are the groups of black and white boxes seen at right. QR codes are similar to barcodes. Where barcodes have one dimension of information, QR codes have two (horizontal and vertical). Barcodes are a row of lines, and QR codes are a grid of squares. Bitcoin uses QR codes because they can store a lot of information in a small space, and a camera such as a smartphone can read them. The two QR codes on the Bitcoin note are the public and private addresses, and can be scanned with a number of online tools.
Everyone in the Bitcoin network is considered a peer, and all addresses are created equal. All transactions can take place solely from peer-to-peer, but a number of sites exist to make these transactions simpler. These sites are called exchanges. Exchanges provide tools for dealing in Bitcoin. Some allow the purchase of Bitcoin from external accounts, and others allow trading with other cryptography-based currencies like Bitcoin. Most exchanges also provide a basic "wallet" service.
Wallets provide a handy way to keep track of all of a user's public and private addresses. Because addresses are pseudo-anonymous, anyone can have as many addresses as they want. This is useful for dealing with multiple people, but it can get complicated to manage multiple accounts. A wallet holds all of this information in a convenient place, just like a real wallet would.
Bitcoin adoption and use continues to grow a lot every year. Since 2012, Bitcoin has gained the attention of the mainstream media. Adoption growth has not only happened for consumers, but also for many companies, who are looking to make use of all the advantages of Bitcoin.