- part of code (block) that can be replaceable, portable, and reusable.
- the way to pass data between components.
- be local to a class(pag).
- npx create-react-app my-app
- cd app-name
- npm start
Node.js is an event-based, non-blocking, asynchronous I/O runtime that uses Google’s V8 JavaScript engine and libuv library.


