What is PHP short description about it

          Hi Sharath
                 PHP is now officially known as "PHP: HyperText Preprocessor". It is a server-side scripting language usually written in an HTML context. Unlike an ordinary HTML page, a PHP script is not sent directly to a client by the server; instead, it is parsed by the PHP binary or module, which is server-side installed. HTML elements in the script are left alone, but PHP code is interpreted and executed. PHP code in a script can query databases, create images, read and write files, talk to remote servers - the possibilities are endless. The output from PHP code is combined with the HTML in the script and the result sent to the userýs web-browser, therefore it can never tell the user whether the web-server uses PHP or not, because all the browser sees is HTML
By Bas De Baar

Regards

Is it a licenced product.And what are the prequesits