HTML (HyperText Markup Language) is the most basic building block of the Web. It defines the meaning and structure of web content. Hypertext" refers to links that connect web pages to one another, either within a single website or between websites. Links are a fundamental aspect of the Web. By uploading content to the Internet and linking it to pages created by other people, you become an active participant in the World Wide Web. HTML uses markup to annotate text, images, and other content for display in a Web browser.
Cascading Style Sheets (CSS) is a stylesheet language used to describe the presentation of a document written in HTML or XML (including XML dialects such as SVG, MathML or XHTML). CSS describes how elements should be rendered on screen, on paper, in speech, or on other media. CSS (Cascading Style Sheets) is used to style and layout web pages — for example, to alter the font, color, size, and spacing of your content, split it into multiple columns, or add animations and other decorative features.
JavaScript is a programming language that adds interactivity to your website. This happens in games, in the behaviour of responses when buttons are pressed or with data entry on forms; with dynamic styling; with animation, etc.