With someone, the definition of Bitcoin is too hard to understand so I wonder whether we have a more simple way to explain to them? 
How to determine bitcoin (bitcoin, btc, Btk, bitcoin) in simple words? This is a new generation of decentralized digital currency, created and operating only on the Internet. It is not controlled by anybody, the currency issue occurs through the work of millions of computers around the world using a program for calculating mathematical algorithms. This is the essence of bitcoin.