The World Wide Web or WWW is the name given in 1990 by Tim Berners-Lee of CERN to his proposal for an Internet-based hypertext system. This would link together behind a single, easy-to-use interface the various information resources spread around the Internet, and accessed using many different systems and protocols.

The invention that weaves everything into a single Web in the WWW was devised by Ted Nelson in 1965: hypertext. In hypertext any word can be associated with a link that points to some other piece of information. So as to be able to display hypertext, Tim Berners-Lee developed a description language called simply Hypertext Markup Language, HTML for short. This was based on SGML (Standard Generalised Markup Language), an extensive structured document-description language used in publishing. The basic idea behind HTML is to describe the structure of a document, for example, by saying which part of the text is a heading, emphasised words or a quotation, and allowing the way these are finally displayed to depend on the user's program and display device. This means that a sight-impaired person can listen to an HTML document on a terminal fitted with a speech-synthesiser, while someone with a graphic user interface can view the same document as text adjusted to fit his or her screen.

So that HTML can be used to create a worldwide hypertext web we, of course, need an unambiguous way of defining links to other documents or other Internet resources. This is done using a Universal Resource Locator, or URL, which is made up of three parts. The first part defines the data transfer method or protocol, such as:

The second part of a URL generally gives the address of the computer where the desired service is, and may also include qualifiers such as a user ID or gateway number. This makes it possible for browsers to work out with which site they are supposed to set up a TCP/IP connection. Examples:
open a connection with the FTP service on the FTP.FUNET.FI computer.
Open a terminal connection to the Finnish National Bibliography FENNICA database
Start up the e-mail function to send a message to the address
Establish a connection with the CSC's homepage

And finally the last part of the URL contains the internal reference on the server in question. This reference can be a file pathname or even database-search parameters. For example, finds the computer, goes to the directory /suomi/funet/ and opens the file there called funet-esittely.html
The keyword 'FUNET' entered into the NWI.FUNET.FI search engine is automatically converted into a URL like the following one, containing the database search parameters:
The end section of this, starting from where it says lang=fi, consists of parameters to be entered into the program nwisearch.tcl for it to carry out a search. Many big WWW websites are nowadays also constructed individually for each user using a database.
In the future, the aim is to give network resources URI identifiers, which correspond to the ISBN numbers used for printed publications. These will make it possible to find a resource even if it has changed server or been copied to various parts of the network.