1. How Internet Search Engines Work
Database
Server
Web Page
URL

2. Database
A database is a structured collection of records or
data that is stored in a computer system. The
structure is achieved by organizing the data
according to a database model.

3. Server
Server (computing), a server application, operating
system, computer, or appliance

4. Web Page
A web page or webpage is a document or resource
of information that is suitable for the World Wide
Web and can be accessed through a web browser
and displayed on a computer screen.

5. URL
In computing, a Uniform Resource Locator (URL) is
a type of Uniform Resource Identifier (URI) that
specifies where an identified resource is available
and the mechanism for retrieving it.

6. Reference
Wikipedia:
http://en.wikipedia.org/wiki/Main_Page