I want to know the technology used in ODOO(Openerp) to send POST and GET data without refreshing the page: because I don't see any AJAX code !!
Take a look at the web addon
Of particular note would be
The js directory mentioned above (i am sorry there is a lot there). Defines how the standard ui widgets work (and much more). Most of the files are reasonably named to give you an indication of what is going on in each file.
You will also want to look at the framework directory within the above noted directory.
There you will find
ajax.js which (you guessed it!) is the Odoo ajax module.
NOTE: The above directories are similar in Odoo8 however Odoo9 and Odoo10 have the above structure. Odoo8 does not have an ajax.js (to my knowledge) .