Ethereum lost $17.5 billion in market value in 4 weeks
Most people have heard of Bitcoin. It is a "highly volatile" peer-to-peer technology to operate with no central authority or banks; managing transactions and the issuing of bitcoins is carried out collectively by the network. Bitcoin is open-source; its design is public, nobody owns or controls Bitcoin and everyone can take part. See: https://bitcoin.org/en/
Ethereum is another peer technology similar to Bitcoin. See: https://www.ethereum.org/
Each are catching on on popularity as you may have seen Bitcoin was used as ransom for cyber attacks with WannaCry when it hit 200,000 computers in at least 150 countries.
Also, if you know the story of Mark Zuckerberg you will recall the Winklevoss twins. They recently wanted to start a Bitcoin ETF which the Securities and Exchange Commission rejected citing a lack of regulation and surveillance-sharing agreements between exchanges. See: http://www.cnbc.com/2017/05/25/bitcoin-flying-as-etf-gets-second-shot.html
It is an ever changing world in which we live in but the bull market continues.