ParameterA parameter is a constant with a variable value which is passed into or out of a program, subroutine, or across an interface, whenever code components communicate with each other.
If the term parameter makes you vaguely uncomfortable in a way you can't quite pin point, it's probably due to the fact that it's a familiar component in the mathematical equations you may have struggled to understand years ago. In mathematics, a parameter is a constant with changing values. In computer science, parameter refers to an element of communication in the language of data exchange. Parameters are like the words of our verbal and non-verbal languages; a change in the value of a parameter changes the message given to the application with which the parameter is sent to communicate. It applicable to all forms of data exchange which require communication between two or more components.
Thus, the term parameter is relevant to the WWW user in many ways. Anyone who wishes to perform a query on a Web search engine must first define the parameters of the search. The key words specified in this instance communicate to the search engine what exactly you want to find out. Those who have gotten strange results from a search know the importance of learning how to communicate effectively with the engine by providing relevant and truly descriptive parameters.
Parameters are also used in establishing URLs. Each element of a URL narrows down the location of a WWW page a little more. Therefore, each section of a URL is a parameter which communicates to the browser which file you wish to retrieve. Writers of HTML documents have undoubtedly learned the necessity of treating the parameter with respect. A parameter written even the tinniest bit incorrectly will lead to a mail-box being filled with angry messages from users unable to access promised information.