The final months of 2017 brought all-out bitcoin mania. The value of the digital asset soared near $20,000, then settled back down below $15,000, and is up nearly 1,500% this year; Coinbase, the bitcoin brokerage, surpassed 13 million users and briefly became the No. 1 smartphone app on the iOS App Store; and mainstream financial exchanges like CME, Cboe, and Nasdaq are all rushing into bitcoin futures trading.

So you might be feeling left behind if you’re still wondering: What exactly is bitcoin?

But you’re hardly alone: even amidst the frenzy, cryptocurrencies are in their infancy, and many, many people hearing about bitcoin still don’t fully understand what it is, what it’s used for, whether they should buy it, and how to buy it.

Here are some answers.

What is bitcoin?

Bitcoin, the technology, is open-source software for a decentralized, peer-to-peer payment system. Bitcoin, the digital asset, runs on the bitcoin blockchain, a decentralized public ledger where all bitcoin transactions get permanently recorded.

Bitcoins can be bought, sold, or traded, like a commodity, or used as payment for hard goods, like a currency. Many people call bitcoin a “digital currency” or “cryptocurrency,” but these days, no one is really using bitcoins to buy things. Instead, people are buying and holding bitcoins as a speculative investment. For that reason, a more apt term for bitcoin right now is “digital asset” or “digital token.” (See the above video.)

If you want to buy bitcoins, you can use an exchange like Coinbase, Kraken, Bitfinex, or Bitstamp, to name just a few.

Bitcoin was created in 2009 by someone (or someones) using the pseudonym Satoshi Nakamoto. It still isn’t known who that was, or how many bitcoins that person or group still holds.

What is blockchain?

Bitcoin, the token, runs on the bitcoin blockchain, an immutable digital ledger. Every single transaction done in bitcoin is recorded, permanently, on the bitcoin blockchain. Think of the bitcoin blockchain as akin to the borrowing card inserted in the front of a library book, with all the borrowers listed. (See the below video.)

The transaction data is recorded on the blockchain in bundles, called “blocks,” by “miners” who use expensive machines to mine, or upload, the blocks. The machines mine by solving complicated computations in real time (and they generate a lot of heat in the process). Miners are rewarded with a tiny amount of bitcoin every time they do so. That’s how new bitcoin gets created—the bitcoin supply is capped at 21 million coins, and 16.7 million coin have been mined so far.