[TxMt] code coloring/language scope question

[plastichairdoo]

hi there - I know that there's a way to use different code coloring for different parts of a document according to the scope of the section - for example when I have Javascript code in a <script> tag or CSS in an HTML doc etc etc. 
I read through the Textmate Help and found that it is possible but admit to being rather confused by how it works. 
is there a tutorial of any kind? 
or an example theme I could look at that would illustrate the process?
thanks,
bennett