Bitcoin is the first cryptocurrency: a payment network based entirely on cryptographic algorithms rather than trust in a centralized institution. But because Bitcoin is an open-source project, it’s not hard to spin off competitors based on the same basic concepts. Today there are dozens of them, commonly known as “altcoins.”

One of the first, and still the most popular, is Litecoin. It boasts a shorter transaction time (2.5 minutes compared to Bitcoin’s 10) and a different algorithm for mining that makes it easier for ordinary users to participate and earn coins. In November 2015, the value of all litecoins in circulation is around $200 million.

Other relatively popular (but still tiny) currencies include privacy-oriented Dash and Dogecoin, a currency based on a silly internet meme. These altcoins are worth less than litecoins and a lot less than bitcoins. Indeed, the value of all bitcoins in circulation is around 9 times the value of the top 100 altcoins put together. Bitcoin is by far the most important cryptocurrency.