No, these aren't actually bitcoins. (credit: fdecomite)

This explainer originally ran in early December. With continued high interest in bitcoin, we're republishing it with updated prices.

This week, bitcoin has gone through a wrenching selloff, falling from a high of $19,500 earlier this week to below $13,000 on Friday.

In recent months, the currency's astonishing gains—it was worth less than $1 in early 2011—and subsequent decline has caused a lot of people to wonder if they should be paying attention to the technology. While almost everyone has heard of bitcoin at this point, many people are fuzzy on the details: what is a bitcoin, exactly? How do I buy some? What would I use it for?

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