The HTTP handler is used in web services handle the
information between web browser and web server.

It as a  program.(or handler, or module), it execute some 
code when the user send some request. An .aspx page can be 
thought as a HTTPHandler too, which implements more 
functions.

when the incoming zHTTP request is processed by the This 
PageHandler factory it creates a instance of HTTPHandler 
class.HTTPHandler  are >net components responsible for 
serving HTTP requests.These comp inherit from IHTTPHandler 
interfaces and have 2 methods
(Isreusable,ProcessRequest).The processrequest method id 
the heart of the HTTPhandler class and repsonsible for 
processing requests.The Isreusable method checks whether 
ths instance created by the Pagehandlerfactory can be used 
again to server these type f requests.

Once the processing is completed ,the HTTPHANdler compiles 
the code and generates the corresponding output and returns 
it to the browser

Http handler is a piece of code or aprogram for respond to 
the incoming http requests from the server side.