What exactly is the difference between Web3, blockchain, and cryptocurrency⌗

You can think of blockchain and cryptocurrency as technological implementation details, and Web3 as the communities, businesses, and social relationships that form on top of that technology. A similar analogy would be the original World Wide Web, which could have been construed as a rebrand of the underlying technologies of HTML over HTTP over TCP/IP. Those protocols have served as the foundation for virtually all web content for the last 30 years, but it’d certainly be unfair to describe “the Web” as merely a rebranding of HTML/HTTP/TCP/IP since what happens on top of those protocols is much bigger than just the protocols themselves.

Using blockchain as a database to store personal data in account?

Authentication⌗

Before Web3⌗

  1. Username and password
  2. OAuth protocols(namely OAuth2)

Web3⌗

  1. Wallets that use asymmetric cryptographic algorithm(public key and private key).
  2. Smart contracts enables advances features, like recovery your lost key.
  3. MetaMask.