Say you want to learn more about organic gardening. You then get a list of subcategories. At any point you also have the option of using a key word to search and you further have the option of searching all the sites catalogued by Yahoo, or just those sites listed in that subcategory. Every index catalogues differently. You can also check to see if there is a Web Ring on your interest.
Web rings are sites of a common interest linked together.
The gardening ring is not specifically about organic gardening. Some search sites, for example Ask Jeeves , allow you to ask a question in plain everyday language. It will also give you links to where those answers can be found. You use a search engine, like HotBot , by giving the engine key words to look for. Engines search the Internet in various ways.