Techopedia explains
Hypertext Markup Language (HTML)
Some new to web development mistake HTML for a programming language when in actuality it is a markup language. HTML needs to be used in conjunction with other technologies to "do something" as all HTML really does is organize a document. On the client side, Javascript is used to provide interactivity, while on the server side, a web development platform such as Ruby, PHP, or ASP.NET is used. When a web developer builds an application, the work is performed on the server, and raw HTML is then sent out to the user. The line between server-side development and client side development is blurry with technologies such as AJAX.
HTML was actually never designed for the web as it exists today -- after all, it is just a markup language and has severe limitations in terms of control and design. Numerous technologies have been used as a work-around for this issue, the most significant of which is the cascading style sheet (CSS). The long term solution is, or hopefully will be, HTML5, which is the next generation of HTML that allows for more control and interactivity. As with any development on the Web, the move to standards is a slow and arduous process and web developers and designers need to make due with technologies that are currently supported. This unfortunately means that basic HTML is still going to be around for some time.