I'll make it somewhat easy on you.
If you're a shopkeeper, it's nothing you really need to worry about. If you're interested, keep reading.

Affiliates can promote your product through lots of channels.
Linking to your products.
-They can link right to your product or section in your shop.
-They can link right to your product or design in the marketplace.
-They can link right to your product or section in the "
green version" of your shop. That's a stripped down version of your shop that CP offers to help affiliates and shopkeepers. It doesn't have any of the section descriptions or custom html, so we all have less chance of a "leak". A "leak" is anything that can distract a shopper from purchasing, like flashy buttons or links to other domains, etc.
-They can create or purchase scripts that basically pull the products into their own wrapper where the product basically stays on their site until checkout at CP.
Now, to find the products they want to promote:
-They can search the forums for people posting their designs.
-They can ask for submissions in the affiliate forum if they are looking for something in particular.
-They can search through the marketplace themselves to find things they like.
- They can use third-party tools that use a product feed provided by CafePress to pull shops or designs based on search keywords. Cafepress allows people to access their database of products in order to help sell them.
I think that covers it. We do all of those depending on the affiliate shop.

For votewithyourshirt.com, I am/will be pulling products to feature on the front page for voting, but I also pull products in with the search terms. We keep them in our wrapper until the checkout.
Does that help?