Hypertext Markup Language, a standardized system for tagging text files to achieve font, color, graphic, and hyperlink effects on World Wide Web pages and Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation of a document written in a markup language.

HTML5 will load much quicker than its older brother because it implements Web Sockets. We have more flexibility in creating our website. This language is growing and will only result in more, new, better and faster features that will leave old websites looking outdated.  HTML5 includes detailed processing models to encourage more inter operable implementations; it extends, improves and rationalizes the markup available for documents, and introduces markup and application programming interfaces (APIs) for complex web applications.

Cascading Style Sheets (CSS) offer increased flexibility in the presentation of website content. In essence, it just makes everything prettier. CSS3 offers some exciting new features to enhance the appearance in our websites.
HTML5 and CSS3 together will give you some serious designer credibility.