A search directory is usually associated with Search Engines as a place to query searches.  When its a database of websites that are associated strictly by categories.  Categories range from Autos to Zoos.  With a lot of other categories that may be minor categories within the major ones.

When you submit your site to the directories you have to make sure that you:

What User Based Directories may use to evaluate your site that you are attempting to list.

1. Pick the proper category that your site will fit into.
2. That you choose descriptive Titles and Descriptions for your listing.
3. Title and Description are relevant to the content within your site and links you point them to.
4. Make sure that your domain names match the site title to avoid your site from being listed. They are user based databases.
5. Make sure your site is secured for online purchases, use Paypal if you don’t have proper online ordering capabilities.
6. Proper contact information within the site, usually 1 click away or on the home page.
7. If you are associated with any certs that you have a link on your home page to show security.
8. Make sure that all the content on the site will show properly on all computers that may use a search engine or directory.
9. Make sure all code is free of errors including all JavaScript.
10. Make sure all internal links that are pointing to any internal pages work properly and have reasonable load times.

Here are some directories that you can use for free to get your site going:

• Yahoo Directory
• The Open Directory DMOZ
• Google Directory
• SearchSite
• Or you can check out SearchEngineWatch for a detailed list of directories.

Search Directories are a great starting ground for 2 things, links and possible searchers looking for more links or for a particular product or service.