Some newsgroups contain relatively more valuable information than others. A few newsgroups are moderated. They also eliminate duplicate postings. The newsgroups are like the robots in that they contain a large amount of information often with a lot of junk among the jewels. The primary thing you must understand about these search engines is that robots produce indiscriminate quantity while directories produce small amounts of quality information resources.
Robots deal in millions of web sites.
Directories deal in thousands, or at most, tens of thousands of websites. Robots collect everything and anything, the junk as well as the jewels of internet information. The directories strive to collect mostly jewels, although some are more discriminating than others. In fact, you'll find some directories that are totally indiscriminate and evaluate a web site no more than a robot does. Some robots are more discriminating than other robots.