Bitcoin was created in 2010 by an 'anonymous' developer called Satoshi Nakamoto. He designed a system called a Blockchain: a network of computers that keep track of every single transaction. (Banks usually do this on a single, powerful server.)
As of today, Bitcoin is considered a currency, just like the US Dollar or the Euro. The main difference is that instead of assigning a value to a piece of paper, each Bitcoin is a computer file. It's also decentralized. No one bank or country defines the rules for Bitcoin. Instead, it's a community of people (and their computers). Like the Euro or Gold, Bitcoin is worth what the buyer and the seller 'agree' on. As of October 20th, 2017, a Bitcoin is worth $5,990.
We've created a presentation where we explain Bitcoin's history. Take a look: