In a nutshell HTML provides the overall structure of a web document. There have been many versions of html with html5 being the latest. The idea is to give the document semantic meaning and then you use CSS to give the presentational effects such as color, fonts layout and so on. I have found that w3schools offers a good overview with practice sessions for each topic. I also found a 15 minute video on the basics of HTML from youtube.

Sources

www.w3schools.com
http://www.youtube.com/watch?v=Ggh_y-33Eso