What is a postback

                All the web applications are running on Web Servers. Whenever a user made a request to the web server, the web server has to return the response to the user. PostBack is the name given to the process of submitting all the information that the user is currently working on and send it all back to the server. Postback is actually sending all the information from client to web server, then web server process all those contents and returns back to client.

               A postback originates from the client side browser. When the web page and its contents are sent to the web server for processing some information and then, the web server posts the same page back to the client browser. Normally one of the controls on the page will be manipulated by the user (e.g. button click), and this control will initiate a postback. Then the state of this control and all other controls on the page is Posted Back to the web server.