As we might or might not already know, a search engine is a software system used to search on the Web for texts, images, and other type of files containing information. These search engines are classified into 3 different types:

1. Crawler-Based Search Engines
2. Human-Powered Directories
3. Mixed Results obtained by the called “Hybrid Search Engines”

Crawler-Based Search Engines

This type of search engines named crawler-based after the way they spider the web, they automatically create their listings. To finally add the pages to the database of the search engine, the crawler pulls out keywords by digging through individual web pages. Once they’ve crawled the web, people have to search through the results the search engine threw. How the results are listed is affected by the web pages features: titles, body, etc. Changes can be applied on the web pages by their admins to manipulate the order in which they appear.

These search engines are a good option when you got defined a specific topic for your search. Some examples of this kind of search engines are:

Human-Powered Directories

As you can tell by its name, human-powered directories depend on human editors for its listings to be created. This type or search engines is useful when you are interested in getting results on a general search topic. Some examples of human-powered directories are:  Yahoo Directory, Open Directory and Look Smart.

To use a human-powered directory it has to been submitted shorts descriptions in all sites to the directory. It can be done by the person who owns the site or by editors as a review. The better the site, the more likely this will be to get reviewed, which is what’s taken in count when making a search, the matches between the search running and the descriptions given to the websites. Unlike search engines Crawler-Based, on directories the listing is not affected by the website as it is, just by the descriptions submitted.

Hybrid Search Engines

Nowadays, mixed results from crawler-based search engines and human-powered directories can be obtained by using a third type of search engine called Hybrid.  Search. Although it is usual that a hybrid search engine will rather show results from one type of the two listings over the other one, it does present both. One example of this kind of search engines is MSN Search, Yahoo.com, Google.com.