feeder, the easiest way is to start with the simple concepts and build from there.
>what, exactly, is a theme?
The theme is nothing more than the basic concept or idea that will pertain to the whole site - the big picture. Then, the individual parts fit into that basic concept, like the pieces of a puzzle fit together to make up the whole thing.
Pictured in the most elementary terms, say the theme is your hand. You've got the palm, the center or the main part. Then, there are five fingers - related and each slightly different in use and appearance, but they still make up part of your hand.
The theme is my hand (index page, establishes the theme.)
When I grasp with my hand, the thumb is the strongest finger.
When I point at you, I do it with the index finger of my hand.
The finger on my hand where I wear jewelry is called the ring finger.
The pinky is the smallest finger on my hand.
I can't remember what the finger in the middle of my hand is called.
A little silly and exaggerated, but it all fits together and is part of the whole. The main word is carried across all of the sentences, and even though they all relate to the hand, each has it's own particular meaning and function.
To develop the idea takes research. Keyword research to come up with a big list of related words, then refining it down to the best ones that fit the whole idea of your site. It's centered around what you want to sell or tell.
>how can I control what keywords the search engines will derive from this?
You control it by the way you use the words across the site and on each individual page. How sections develop is that there are a number of pages that relate to one particular area within the whole. Kind of a big branch on a tree (the section) with a lot of little branches and leaves on it (the pages). All put together, they're part of the branch, which is attached to the trunk (the index page or site map). There can be a number of large branches or sections - each slightly different, but consistent with the whole thing put together. The big branches make up what goes into the canonicals - or in the case of some, individual directories on the site.
Even more confusing, or make sense?
(edited by: Marcia at 9:49 pm (gmt) on Oct. 31, 2001)