This weekly update tracks some of the largest cryptocurrencies by market share: bitcoin, Ether, and Tether. We've also included XRP, as it was one of the largest cryptocurrencies when this article began. According to Wikipedia, a cryptocurrency is "a digital asset designed to work as a medium of exchange that uses cryptography to secure its transactions, to control the creation of additional units, and to verify the transfer of assets."

Bitcoin is the world's first cryptocurrency and decentralized digital currency. The first bitcoin transaction occurred in early 2009 and has since grown worldwide. Ether is another cryptocurrency run on the Ethereum blockchain platform and has the second largest market share, despite being the newest of the three with its launch in July 2015.

The third-largest market share of cryptocurrency, Tether, is a token "backed by actual assets" which includes one US dollar, one Euro, or loans to affiliate companies and is controlled by the owners of Bitfinex. It's a controversial cryptocurrency due to its alleged manipulation of crypto pricing. It is called a "stable coin" because it was designed to always be worth $1.00.

XRP, which is owned by Ripple and launched in 2012, was one of the larger cryptocurrencies for some time until new coins joined the market. We've included it here for reference.

Here are four cryptocurrency prices over time along with their trading volume. Data is sourced from Coinbase.com through Yahoo! Finance.

We have also created an index in order to chart these together given their very different pricing history. Notice that Ether tops the chart - the price of an ether has changed the most out of all three cryptocurrencies. Tether has shown virtually no movement due to its "stable coin" feature.