What is JavaScript?

JavaScript is a programming language that is most used in web development as a front-end and back-end technology. If used as a front-end tool (which means it runs in the browser) a developer can combine it with a different back-end tool (which is a programming language that runs on the server) like PHP, Java or C#. But it can also be used as a back-end tool since the existence of JavaScript frameworks and runtimes like Node.js, Express, NestJS and similar.