The most obvious way that directories distinguish themselves is through the amount of information that they accept during the submission process. In fact, submission forms are considerably longer for directories, allowing your personalized descriptions, company name, keywords, contact information and more to be entered, along with your URL and e-mail address, into a category of your choosing. To be located properly, you should list your site in the most appropriate category at the directory. For those who feel that their site's topic is not recognized by existing categories, most directories also provide a space to add a new one. Another major difference between search engines and directories is that directories do not utilize scouts i.e. robots, spiders, etc. to gather web site information for their database.
All directories rely on humans for their listings.
For this reason, your URL will not appear at any directory unless it has been manually submitted. Like wise, humans review sites that are submitted to directories, causing a longer delay for your site to be indexed in their database. Relevancy in directories is based upon your keywords and the words that are found in the description that is initially submitted. Don't try to fool directories with repeated keywords or words that are inappropriate for your service or product. Chances are that you will be caught, rendering your submission useless.