php is a coding language for websites, and can be coded to access databases and return the information to the browser. So you make a tiny change in the database, and everything on your site will update, like magic. It is usually combined with a bit of html to make things look pretty. You can even make a php page that will add info into the database, making it VERY easy to update the site with news, etc.

mysql is a database, sort of like M$Access, but open source, and much better for website use than M$Access.

The two things I listed are entire sets of php pages and mysql tables that you can use to make a site without having to know any of the actual coding stuff.

Bandwebsite - this one is buggy, though, and I don't know how secure it is. Haven't actually tried it myself.

PostNuke - looks to be pretty good so far.

I'm having a slight problem with accessing the database, but it seems to be a problem with my host, not PostNuke, as I get the same problem when trying to access it at all.

Hope that helps.