JavaScript is a scripting language that allows web pages to become interactive. It is used to validate forms, communicate with servers, and add various dynamic effects to web pages. JavaScript is not the same as Java, as it is a lightweight scripting language that can be run directly in web browsers without compilation. JavaScript code is typically embedded directly into HTML pages using <script> tags and can react to various events like button clicks or form submissions. Common JavaScript features include variables, operators, functions, events, and methods to manipulate HTML elements and styles.