React components are reusable, self-contained pieces of code that represent parts of a user interface in a React application. Each component defines its own structure using HTML, behavior using JavaScript (or Typescript), and styling using CSS, if needed.
Components can be classified as functional (using functions) or class-based (using Javascript classes), and they can accept input data via props and maintain their own state to manage dynamic data.
React renders components efficiently by updating only the parts of the UI that change, thanks to its virtual DOM.