why do we need a script manager always when we are using Ajax control?

Question

why do we need a script manager always when we are using Ajax control?

Answer 1

Script manager control is the control that send the scripts to the client. This control is at the heart of all AJAX related functions. It manages all controls in your Ajax enabled page. It also ensures that partial page updates happen as it is expected.

http://msdn.microsoft.com/en-us/library/system.web.ui.scriptmanager.aspx