It's not a sophisticated search. As far as my experimentation has shown, the search field actually searches these 5 areas:
- id/sku
- name
- short description
- description
- keywords
If the search term doesn't appear in one of these areas, the item won't turn up when that term is used. The problem you have to worry about at this point, is how many items will turn up for a certain search term. If you sell different types of knives and a user searches for "knife," then every item you sell will turn up in the search results. Even an item such as "Cloth for Cleaning a Knife" will turn up as it has "Knife" in the title -- the problem here being that the person who searched for a "knife" probably wan't looking for a cloth.
Hope this helps!