In regards to learning about WP there are basically five pieces to consider: CSS – controls the display of your site, like positioning, colors, size, etc.
HTML – provides the basic site structure or “building blocks” PHP – server-side processing, like database queries, getting theme options, etc.
Javascript/jQuery – make changes to the site based on events like mouse clicks MySQL – database used by WP (this would be nice-to-know but not essential)