I'll try my best to write a brief summary in English, but please note that I'll translate it into Simplified Chinese below.

Cryptocurrencies, such as Bitcoin, are digital or virtual currencies that use cryptography for security and are decentralized, meaning they're not controlled by any government or financial institution. They're often used as a form of alternative currency and can be exchanged for traditional currencies like the US dollar. However, the value of cryptocurrencies can be highly volatile and is not backed by any physical commodity or government.

(转载)

加密货币，如比特币，是使用加密技术进行安全的数字或虚拟货币，它们是分散的，不受任何政府或金融机构控制。它们通常作为替代货币使用，可以与传统货币如美元交换。但是，加密货币的价值可能非常volatile，不是由任何物理商品或政府支持。