HTML (HyperText Markup Language) and CSS (Cascading Style Sheets) are programming languages that are used to create web pages. HTML provides the structure and content of a web page, while CSS controls the visual design and layout. HTML uses tags to surround content, such as Welcome to Simplilearn. CSS uses selectors followed by a declaration mark, such as `header{ background-color: green; }`.

JavaScript (JS) is a scripting programming language that runs on web browsers to enable specific features on web pages. It's used to create dynamic content, improve browser compatibility, and enhance the user experience. For example, JavaScript can enable features like: Interactive maps, Animated graphics, Scrolling video jukeboxes, User registration, Online shopping, Sharing photos, and Writing messages.