Currently, there are billions of pages on the World Wide Web and only about 2% of Web traffic accesses any of these pages directly as "well known destinations". So what accounts for the other 98% of Web traffic, and how do people find all the rest of the not-so-well-known pages? The answer: Search engines and search directories.
Search engines and directories attempt to sift through every page on the web, either by automated means or by human review, and catalog the contents of these pages. No one engine or directory can handle all of this content, but collectively they have analyzed most of the content on the Web. It is a daunting job - they never actually evaluate EVERY page on the Web, but they DO find the vast majority of sites and pages.
There are hundreds (if not thousands) or search engines and specialized directories out there, but only about the top two dozen or so account for 98% of Web traffic. Does this figure sound familiar - yes, it is the SAME 98% mentioned above. All of the other search engines together account for only "trace" amounts of traffic!
What all of this means is that whoever markets your web site needs to be aware of the realities of the search world and be sure your site is well represented in these "top two dozen" engines and directories, as well as any appropriate specialty directories.