JavaScript is a text-based programming language used both on the client-side and server-side that allows you to make web pages interactive. Where HTML and CSS are languages that give structure and style to web pages, JavaScript gives web pages interactive elements that engage a user. Incorporating JavaScript improves the user experience of the web page by converting it from a static page into an interactive one. To recap, JavaScript adds behavior to web pages. JavaScript is most known as a web-based language because it's native to the web browser. The web browser can naturally understand the language, like how a native English speaker can naturally understand English. JavaScript is versatile for various applications, such as software, hardware controls and servers.
Developers use JavaScript to build complex interactive websites and browser games and to connect servers to websites and web applications. Because of this versatility, it's easy to see why this language is the world's most commonly used programming language.
