First, a definition. Meta Search - A search tool that queries several search engines and/or web directories simultaneously and returning the results in a single merged list without the duplicate links.
Confused? Let me give you an example. Let's say there is a meta search engine you have recently found that searches two engines, let's say Google and Yahoo. It searches both of these search engines and then returns the combined results to you, without any duplicates (results that appear on both engines). Sounds neat , huh? Well, there are pros and cons with meta searching that the user should be aware of in order to make his searching as productive as possible.
The Pros of Meta Searching
Meta searching is fast, and saves considerable time for the user since you may query several engines and directories simultaneously rather than typing in a single query in every search engine that you wish to get results. Webmasters will find meta searching extremely valuable in checking their site's page listings, backlinks, keyword ranking, and other site statistics in several search engines. Other professions that are research-oriented would also benefit greatly from meta searching. Professions such as educators, scientists, legal professionals, college students to name just a few.
The Cons of Meta Searching
Most, not all, meta searchers do not allow site submissions. This is because most do not maintain their own database of page listings. They simply get results from other search engines. Because most meta searchers query anywhere from 4 to 12 engines and directories simultaneously, and not all of them will allow Boolean searching, many meta searchers therefore will not allow Boolean searching. (Boolean seaching is the use of operators such as AND, OR, quotation marks, and plus/minus symbols.)
The Meta Search Engines
Meta search engines come in a variety of forms. The standard meta searcher simply queries several engines and returns the results on a single page. Others return results from each engine queried separately, either dividing them on a single page or opening multiple browser windows, each containing the results from a different engine. And another type, generally known as all-in-one search, also allows you to query many different engines, but just one engine at a time.
Standard Meta Searchers: Old School
These are some "oldies but goodies." The following list includes some notable examples of standard meta search engines, many of these having been around for years and have remained quite popular with the searching public.
Meta Searchers: New School
Below you will find some excellent examples of newer meta search engines. Many include nifty features for advanced searching, such as clustering. Clustering search engines gather results into groups around a certain theme, or in some cases just provide you with related keywords that perhaps will aid the user to zero in on your goal. Others offer the user the ability to set the bias of each search engine the meta searcher pulls results from. For example, telling it to weigh results more from Yahoo than from Ask Jeeves.
All-In-One Search Pages
Below you will find some excellent examples of what I call all-in-one search pages. These are not technically meta search engines as they only allow the user to search one engine at a time, but they certainly provide a valuable service to the web searcher.
Conclusion: There are several advantages to using meta search engines, the most obvious advantage being the ability to get results from multiple search engines without having to visit each in turn. Meta searchers in general are fast ways of getting information on things broad in scope. And finally they are important in allowing the user to see how the various search engines return results on the same query.