Bitcoin is the first ever decentralized cryptocoin built on top a blockchain. It was developed by Satoshi Nakamoto, an anonymous group of people, in 2009 as an open-source project.
The Bitcoin blockchain can be viewed as a book. Each page number has a signature that validates the content of the page. This signature cannot be reversed and is calculated using an algorithm called SHA-256. This means that we can compute the A256 signature from any content but cannot get it if we don't know its SHA256 signature. Let's return to the book example. If we take a page out of the book, it is easy to see that a page has been missing. It is the same with adding a page that isn't there. The pages are copied among the members of the chain. This is why the Bitcoin Blockchain can be considered a distributed network.
Bitcoin is an open-source project that is maintained by a team of over 580 contributors. Github contains the code for the chain. Bitcoin's main purpose was to allow trusted, low-cost transactions between individuals and businesses all over the globe. Today, Bitcoin payments are accepted by more than 100.000 vendors. There are between 2.9 million and 5.8 millions of users who use Bitcoin cryptocurrency wallets. The price of Bitcoin can fluctuate due to speculation. It has changed by more than +/-20% in one day.