@shahi baba, it's history It started in 2009 after the stock market crash. Japanese/American computer scientist Satoshi Nakamoto came up with the idea of peer to peer money transfer. Soon the idea started action and thus a startup was formed in New York City.

The idea is that the value of the money is backed by the Central Bank that provides monetary value to it. Thus for any transaction we make we pay certain amount as commission. The idea that bitcoin came up with is to eliminate the middle man so the cost of commission is eliminated. You can transfer money from one country to another for free as well as do transactions for free.

The idea of bitcoin is that using blockchain or encryption, the transaction of people are in distributed system not centralized. That means your history of transaction is save distributed online where it is available to public ledger but your identify is hidden. Thus it can be safe from hackers.

Well the value that it gained is because people started believing on it as the money of future and started investing on it. The question is still debatable if it will be the digital money of future or it's bubble will burst is yet to be unfolded. Hope it helps to give you some background.