Math

The world wide web (www) is a huge set of interlinked documents, images and other resources. Linked by hyperlinks, they enable the web servers and other machines that store originals (and cached copies) of these resources to deliver them as required when sought by a visitor.

A web directory service (like this one) is a shared information infrastructure for locating and organising websites. Human edited directories (like this one) are often targeted by SEOs on the basis that links from reputable sources will improve rankings in the major search engines.

The biggest advantage that general internet and business directories can offer is for search engine purposes. In short, being listed on a wide spread of IP blocks, across on-topic pages, and listed with other quality sites, can be highly advantageous for search engine purposes. Web directory submissions are just one way you can increase the impact of your website through search engine optimization.