Bitcoin is one of hundreds and still may be thousands of crypto currencies on the internet. Crypto currency is a digital currency that uses cryptographic technology for security that makes it unable to be falsified. The price value of cryptocurrency is purely determined by market forces, namely the requests and offers of users of this technology
Bitcoin become special because of its characteristics. When you look on the market you will see the big difference on its price compare to other cryptocurrency. Hence it was more popular which can be directly converted into fiat in order for many people to used it in their daily lives.