HTML - Hyper Text Markup Language (HTML) is essentially text that the web browser can read and render in a human readable format. If you want to see HTML, right-click the web page and choose view source. HTML5 is the current version of HTML. The HTML5 standard improves native support of multimedia, offline database, forms, geo-location, and more in the browser. The primary benefits to users and developers is the reduced dependency on 3rd party plug-ins, improved search engine discovery, and a more mobile device friendly mark up.
CSS - Cascading Style Sheets (CSS) are used by the browser to style rendered HTML. For example, CSS can tell the browser to display all links on page in the color red. CSS3 refers to the latest version of CSS and like HTML5, improves the native support of animations, style selectors, multi-column layouts, text effects, and more. The primary benefits to users and developers are reduced dependency on 3rd party plug-ins, improved cross browser compatibility, and allow for a more mobile friendly browsing experience.