For subjects in John Jay mission field start with the Library's list of Selected Internet Resources . For other subjects find a good starting point using one of the directories listed below, or discovered through a newsletter or discussion list in your field.
Search engines have three major elements.
First is the spider, also called the crawler. The spider visits a web page, reads it, and then follows links to other pages within the site. The spider returns to the site on a regular basis, such as every month or two, to look for changes. Everything the spider finds goes into the second part of a search engine, the index. The index, sometimes called the catalog, is like a giant book containing a copy of every web page that the spider finds.