HTML5 is a core technology markup language of the Internet that is used for presenting and structuring content for the World Wide Web. This is the complete fifth revision of the World Wide Web Consortium’s (W3C) HTML standard.
HTML 5 mainly aims at improving the language with support for the latest multimedia keeping it consistently understood by computers and devices (parsers, web browsers etc.) and easily readable by humans.
HTML5 is a response to the fact that the XHTML and HTML in common use on the World Wide Web are a mixture of features that have been introduced by various specifications along with the ones introduced by software products like web browsers and the ones established by common practice.
HTML5 has been designed so that old browsers may safely ignore new HTML5 constructs. The HTML5 specification provides detailed rules for parsing and lexing, with the intention that different compliant browsers produce the same result for an incorrect syntax.