Search Concepts

Search Concepts : The most important thing to learn about the web is that there is no central registry, no traffic cop, no chamber of commerce, no one place where you can go to find what you are looking for. There are, however, some sites trying to do their best to fill that role.

The key thing to remember about these sites is that they are all different. Understanding their differences will give you a chance to make your searching efforts much more effective!
Different Databases
Each search tool on the web maintains it's own database of web sites. There will, of course, be overlap between the various search tools but it is important to remember that just because you didn't find it on one tool doesn't mean it's not on the web. No one search tool knows about all the web sites -- in fact the search tool that knows about the most web sites only knows about 34% of the 320 million web pages.
Different Methods
Each search tool has its own way of searching its database such as category searching (Yahoo), full-text searching (Alta Vista), concept-based searching (Excite), and multi-threaded searching (Saavy Search). Depending on what you are looking for and how you approach your search, you may find that one tool is more useful to you than another one.
Different Results
Each search tool will report the results of your search back to you in a different manner. Some will give you clues as to whether or not the search result is really what you are looking for which can save you time and effort.
Different "Helps"
Most of the search tools out there offer you some help in refining your search. Some of these "helps" will be more helpful than others.