LONDON (AP) — The price of a single bitcoin has pierced the $10,000 level and some experts say it could rise further. The world's most popular virtual currency allows people to buy goods and services and exchange money without involving banks, credit card issuers or other third parties.

It has a fuzzy history, having been used by hackers to demand ransom and for the purchase of illegal drugs online. But recently it's become more popular with a different crowd: speculative investors.

As its price keeps rising, here's a brief look at bitcoin.

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HOW BITCOINS WORK

Bitcoin is a digital currency t...