In the Beginning, the HTML code, CSS Styles, functionality code and site content were all mixed together
The end result was that viewing the guts of a website was like reading Babylonian Code, everything mixed together. On the plus side, the result was that you needed special people that could decipher all this mess. Not only to initially create it but also to maintain and update it, and you paid dearly for their services.
Step One: CSS Style Sheets finally separated Structure from Style, huge improvement
A style sheet could suddenly define universal styles for every element within a site, and the editing of one simple code could change the entire look of the site.
CMS then separated Content from Structure
The Content Management System ( CMS) Dashboard User Interface for placing content was as revolutionary as the move from DOS to Windows.
CMS now looks after all the other elements, so you can focus on Content
Themes provide the basic Structure and Style, and widgets provide the site Functionality or Utilities. The User then uses the Dashboard for Content addition \ Media Library creation and designing a Site Navigation Menu structure.