Terser is a JavaScript parser, mangler, and compressor toolkit for ES6+ code. It's widely used to minify JavaScript code, reducing file size for faster website loading times. Terser supports advanced optimization techniques like dead code elimination, variable name compression, and more. A crucial tool for front-end developers looking to improve website performance and optimize code for production environments. It's a robust successor to UglifyJS, known for its enhanced ECMAScript support.