PPT Slide
Search Engine Varieties - Directories
Directories index web sites into groups and categories that are intuitive to navigate. Everything is done by human hands: entering, reviewing and indexing. These services are logically arranged, but they capture a much smaller snapshot of the pages on the WWW (when compared to Spiders/Robots). Yahoo!, the largest of the Directories, boasts only 500,000 sites.
A site is either included by those at the directory or submitted by the site maintainer/interested party.