Bitcoin is the first decentralized crypto ever built on a chain of blocks. 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 the previous page. This signature is calculated 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. Returning to the example with the book: if we tear a page out of the book, we can easily understand that a page is missing. The same goes for adding a non-existent page. All pages are copied between members of the chain, which is why Bitcoin Blockchain is considered a distributed network.
Bitcoin is an open source project maintained by a team of developers with over 580 active contributors. The string code is available on Github. Bitcoin's main purpose was decentralized, yet reliable, low-cost transactions between people and businesses across the world. Currently more than 100.000 providers accept Bitcoin for payments. And there are between 2,9 and 5,8 million unique users who actively use Bitcoin cryptographic currency wallets. Bitcoin price can be very volatile due to speculation and has changed in the past by more than +/-20% during a single time.