CSS, or Cascading style sheets, is a style language used to describe and define/format how the content of a HTML document will look. CSS is great as it allows you to affect the styling of multiple documents with one sheet. Simply create a reference or link to the desired CSS and it’ll be applied. CSS allows very precise control over the styling of the elements in a document. Through the years, CSS formatting has changed, and features more robust. Today where using the 3rd iteration, or CSS3.
With CSS3, the developer is now able to create transitions, shadows gradients, animations, as well as multi-column and grid layouts. CSS3 also allows some new selectors that allow matching and partial matching on attributes and attribute values. I also allows structural such as applying styling to nth-child, first letter & first line pseudo classes and styling only on element targeted in URL. CSS3 is simply an extension on the already great CSS2 and with it comes just that much more ability and flexibility to styling. Here’s a link to a tutorial that you may find helpful to figuring the ins, and outs of CSS3.
I hope this entry helps. Feel free to check out this link to another entry I’ve done on CSS. There’s addition info and examples on that entry that’ll further assist you in becoming more familiar with CSS. Have a great day.