What is WWW?

(1) What is the World Wide Web?
 The World Wide Web (Web) is a network of information resources. The Web relies on three mechanisms to make these resources readily available to the widest possible audience:
 - A uniform naming scheme for locating resources on the Web (e.g., URIs).
 - Protocols, for access to named resources over the Web (e.g., HTTP).
 - Hypertext, for easy navigation among resources (e.g., HTML).
 - The ties between the three mechanisms are apparent throughout this specification.
(2) URIs
 Every resource available on the Web -- HTML document, image, video clip, program, etc. -- has an address that may be encoded by a Universal Resource Identifier , or "URI".
>>URIs typically consist of three pieces: <<
 - The naming scheme of the mechanism used to access the resource.
 - The name of the machine hosting the resource.
 - The name of the resource itself, given as a path.
 - Consider the URI that designates the W3C Technical Reports page:
 http://www.w3.org/TR
  This URI may be read as follows: There is a document available via the HTTP protocol, residing on the machine http://www.w3.org/, accessible via the path   "/TR". Other schemes you may see in HTML documents include "mailto" for email and "ftp" for FTP.
Here is another example of a URI. This one refers to a user's mailbox:
 ...this is text... For all comments, please send email to <A href="mailto:jean@somesite.com%22%3EJean%3C/A>.
*Note: Most readers may be familiar with the term --"URL"-- and not the term "URI". URLs form a subset of the more general URI naming scheme.

(3) Relative URIs
 A relative URI doesn't contain any naming scheme information. Its path generally refers to a resource on the same machine as the current document. Relative URIs may contain relative path components (e.g., ".." means one level up in the hierarchy defined by the path), and may contain .
Relative URIs are resolved to full URIs using a base URI. As an example of relative URI resolution, assume we have the base URI "http://www.acme.com/support/intro.html". The relative URI in the following markup for a hypertext link:
<A href="suppliers.html">Suppliers</A>
would expand to the full URI "http://www.acmhte.com/support/suppliers.html", while the relative URI in the following markup for an image
<IMG src="../icons/logon.gif" alt="logon">
would expand to the full URI "http://www.acmhte.com/icons/logon.gif".
In HTML, URIs are used to:
 - Link to another document or resource.
 - Link to an external style sheet or script.
 - Include an image, object, or applet in a page.
 - Create an image map .
 - Submit a form .
 - Create a frame document.