Bitcoin meaning

What is Bitcoin?

It is a well-known digital currency(not physical)
in other words i can define it as a logical money which are being  decentralized digital currency, as the system works without a central bank or single administrator.
Bitcoin was invented by Satoshi Nakamoto and released as open-source software in 2009. 
Bitcoin can be exchanged for other currencies products, and services. As of February 2015, over 100,000 merchants and vendors accepted bitcoin as payment.

List of companies which accept Bitcoin 

 Many large companies are accepting bitcoins as a legitimate source of funds. They allow their online products to be bought with bitcoins.
1.Microsoft 
2.Reddit
3.Overstock
4 Expedia
5.Subway
6.PayPal
7.Shopify 
8.Pizzaforcoins