What is React, and what is a component?

React is a library for building user interfaces. I split the interface into components, i.e. pieces that describe what should be shown and how to react to data. A component can be a button, a form or a list of results.

Most often a component is a function that receives data and returns a description of the view. When data or state changes, React recalculates the view it needs and updates the relevant parts of the page. React on its own isn't a database, a server or a complete routing system. We choose those separately or use a framework, e.g. Next.js.