What is bitcoin?
Bitcoin is a kind of digital currency.
You can buy it with dollars or euros, just like you can trade any other currency.
You store it in an online “wallet.” And with that wallet, you can spend bitcoin online and in the physical world for goods and services.
And, of course, bitcoin has a valuation, which you may have heard about because bitcoin's price has fluctuated up and down.
What's different about bitcoin?
Usually, if you pay for something on the Internet, you use a credit or debit card.
That card is connected to information about you, such as your name and billing address.
You can use bitcoin the same way, but unlike with a credit card, the transactions you make with the currency are completely anonymous.
They can't be used to identify you personally.
So you can use bitcoin to protect your privacy. Is that why the WannaCry attackers picked it as a form of payment?
Possibly. Bitcoin has certainly gained prominence in the news media as a technology that can facilitate crime.
But even though the identities of people in a bitcoin transaction may be hidden, the public ledger has increasingly helped law enforcement trace the movement of bitcoins from place to place.