Bitcoin is the first decentralized cryptocoin ever built on top of a blockchain. It was created by an anonymous person or group of people with the nickname Satoshi Nakamoto in 2009 as an open source project.
To understand the Bitcoin blockchain we can imagine a book, where each page number contains a signature that can validate the content of that page and its previous one. This signature is computed by an algorithm known as SHA-256 and cannot be reversed. In other words we can calculate the A-256 signature from some content, but we can’t get content if we know its SHA-256 signature. Back to the example with the book: if we tear out a page from the book, we can easily understand that a page is missing. The same is with adding an inexistent page. All the pages are copied between members of the chain, and this is why the Bitcoin Blockchain is considered a distributed network.
Bitcoin is an open source project maintained by a developer team with over 580 active contributors. The code of the chain is available on Github. The main purpose of Bitcoin was decentralized but trusted, low fee money transactions between people and businesses around the world. Nowadays over 100.000 vendors accept Bitcoin for payments. And there are between 2.9 and 5.8 million unique users who actively use Bitcoin cryptocurrency wallets. The price of Bitcoin can be very volatile due to speculation and has changed in the past more than +/-20% during a single.