There are some directories out there that when you submit a link to it, it automatically gets approved and appears in the directory under the category you asked for. These are perceived as having less value since they are automatic, and a lot of spam can enter them.

This means that many of the better directories (the ones you will receive the most benefit from) are human-edited, or, a human actually looks at each site being submitted and desides whether or not it should appear in the directory. This ensures things are in proper categories, and not stuffed with keywords, and are not just pages full of ads or parked with a "for sale" sign on it.

The better the directory, the more it will help your site.

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