JSX
In plain terms
A syntax extension letting you write HTML-like markup in JavaScript.
Going deeper
JSX lets React developers describe UI with familiar tag syntax that compiles to function calls. It blends markup and logic in components.
Under the hood
Transpiled (by Babel/SWC) to createElement calls; it's expressions, not strings, so it's type-checkable and composable.
Examples
React components, <Button onClick={...}>, Preact, Solid, transpiled UIs.
Think of it like...
Like writing a blueprint and its wiring instructions in one combined document.