1) Search Engines

2) Subject Directories

3) The "Deep" (or invisible) Web

Search Engines- A searchable database of Internet files that allows you to enter search terms, or "keywords", and retrieve information related to that topic.

When should you use an internet Search Engine?

• When you have a narrow or obscure topic or idea
• When looking for a specific site
• When you want to retrieve a large number of documents
• When you want to take advantage of newer retrieval technologies, such as concept clustering, ranking by popularity, link ranking, etc.

Meta-search engines will search several search engines at once, but often times will only retrieve 10% of each search engine's results

Subject Directories - Subject “trees” that catalog or create classification schema for selected websites, organizing sites by subject. This allows you to choose a subject of interest and then browse the list of resources in that category.

When should you use a subject directory?

• When you have a broad topic or idea to research
• When you want to see a list of websites on your topic that experts have recommended and annotated
• When you want to retrieve a list of sites relevant to your topic rather than numerous individual pages contained within these sites
• When you want to search for the site title, annotation, and assigned keywords to retrieve relevant material rather than the full text document

There are two basic types of subject directories: Academic/Professional and Commercial

The Deep Web- The concept of the "deep" web refers to content that is stored in databases accessible on the web, not available to search engines. The only way to access this information is to search the databases themselves.

When should you search the "deep" web?

• When you are looking for very current, dynamically changing information
• When you are looking for information such as news, job listings, airline flights, etc.

There are websites that specialize in collecting links to databases available on the web. Directories are a part of the deep web, for example, "people finders," lists of professionals, patents, and dictionary definitions