Crypto currency is a digital currency that uses cryptography to secure transactions and control the creation of new currency units. It operates on a decentralized network without intermediaries like banks. Crypto currency works through a process called "mining" where users solve complex puzzles to be rewarded with new crypto currency. Popular crypto currencies include Bitcoin, Ethereum, and Dogecoin. Ethereum differs from Bitcoin in its use of smart contracts and its recent transition to a proof-of-stake model called Ethereum 2.0 to reduce environmental impacts. Crypto wallets like Metamask are used to store and transfer ownership of crypto currencies on blockchain networks.