Cryptocurrencies let you buy goods and services, or trade them for profit. Many companies have issued their own currencies, often called tokens, and these can be traded specifically for the good or service that the company provides. Cryptocurrencies work using a technology called block chain. Block chain is a decentralized technology spread across many computers that manages and records transactions. Part of the appeal of this technology is its security. More than 10,000 different cryptocurrencies are traded publicly, according to coin market cap, a market research website. And cryptocurrencies continue to proliferate, raising money through initial coin offerings, or ICOs. The total value of all cryptocurrencies on Aug. 18, 2021, was more than $1.9 trillion — down from April high of $2.2 trillion. The total value of all bitcoins, the most popular digital currency, was pegged at about $849 billion, regaining some ground from recent price lows. These are the 10 largest trading cryptoc