SEO, or search engine optimization, as simply put as I can state, is the art of optimizing your online presence to increase the amount of visitors to your website. You do this by obtaining a high-ranking placement in the search results page of a "search engine." Examples of search engines are Google, Bing, Yahoo, etc. The most ideal result would be to have your business listed as the first result on the first page. That is really very difficult to do, but the closer you can get to that position, the better your chances of having someone find your business, and possibly buy from you.
I have done quite a bit of reading on this subject, and this is what I would recommend for relevancy on Etsy, Artfire, Ebay, or any other venue where your are creating a "listing" to sell a product.
I am going to use Tiger Bead Store as the example and show you what I do.
For Your Title: The first 3 words you use are the most important. You want to use words that you think your customer would put in a google search. Don't worry that your title is not a sentence. You want to use descriptive words.
As an example, here is one of my titles: Cabochons Gemstone Amethyst Faceted Rose Cut 6mm FOR FOUR.
Search engines will look at the first 54-56 characters of your title. It is recommended that you:
-Do not use all capitals.
-Do not use the same word twice in your title.
-Do not use punctuation.
For Your Keywords in the Title:
-What is the item?
-What color is it?
-What size is it?
-Is there more than one to your listing?
-I have also read that it is a good idea to add your business name to the title, at the end.
For the Listing: Reuse the same keywords that you used in the title in the first 2 sentences of the listing. This proves relevancy to the search engines.
For Your Tags: Use those same keywords again.
I hope this helps simplify SEO for you and is helpful.
(This blog post was edited and revised on 8/18/13)