This is just an outline of the various parts of your pages, as broken down in the template tool. Each section will get it's own blog entry later, with each field explained with screenshots. This is basically just a quick intro.

Page Body
This is where you control the background of your site, specifically the background for the main page of your site. All the secondary pages are controlled by the "sub page" fields below. I'll get to them in a minute. This section of fields is where you customize the background for the homepage only. You can choose a colour or image (from your photo gallery, or anywhere online). I really have no idea what the "layer 2" does. Can't figure that one out  :D

Sub Text
This is for backgrounds as well as text, so this section is somewhat mislabelled. Your sub pages are all the inner pages of your site, other than your main home page. The photo gallery pages, your friend list page, etc. Your individual blog pages are considered sub pages, BUT the main blog page that lists your recent ones is controlled by the page body (above).  Most people use the same graphics and/or colours for their sub pages as they do for the main page, but you don't have to.

Sections
There are really 2 kinds of things in this section, adding to the confusion. First of all, what is a module? The modules are the various boxes on your main page. The box showing your blog, your friends, your groups, your comments etc etc.  Those are called modules. I'm not talking about those sections themselves (as mentioned, those are sub pages). The modules are just the boxes displayed on the main homepage. That said, the headers mentioned in this section are the skinny little titles at the top of each module. This will make much more sense with the screenshots.

Menu
The menu is the bar of links that shows up at the top of your page (below the ad banner), but is NOT visible to you if you are logged into your site. The menu is what other people see, or what you see on other people's sites. The links are home, blog, photo gallery etc. When you are logged in, you see a row of tabs for your own site instead.

Custom CSS
This is where you paste in any code that you get from those Myspace layout sites. I cannot offer any guarantees as to the functioning of templates that were designed for other sites. It  CAN work, but they may not be perfect.