HTML (HyperText Markup Language) is the most basic building block of the Web. It defines the meaning and structure of web content. Other technologies besides HTML are generally used to describe a web page’s appearance/presentation (CSS) or functionality/behavior (JavaScript). Basically without html knowledge, you would need a web developer to edit your site, as apposed to CMS, which allows you to control your own site through a admin panel, using pre-defined options.