The images are most likely created using a popular graphics program such as GDlib, Netpbm, or imagemagick. Basically they generate them on the fly or are stored on disk..
Dynamic sites are usually connected to a database some how. THey have a template on how the design aspect should look and then they have the data.
here's an example
most websites have their typical
html - head - title - body what php does is pretty much reuses most of that so you don't have to make thousands of webpages.
Good article on the subject is here. http://www.phpbuilder.com/columns/jesus19990308.php3
also http://www.devshed.com and http://www.webmonkey.com have great articles also.
