HTML is the markup language used to create web pages. This is a mandatory language to know when working on web as it is the common ground to build websites. HTML5 is the most recent version of the language (released in 2014), and has the main objective to make a more semantical code and to separate the content from the form.
HTML5 provides a variety of elements that make the code more semantical, introducing elements such as: header, footer, article, aside, video, canvas amongst the most important. It has the aim to make the screen readers examine the code in a much faster, easier and clear way in order to make it more accessible.
For our developers, the mobile development of website turns out to be easier as most of the mobile browsers are HTML5 ready with the use of the metatags to get the website optimized for the viewport.