Form values are sent over HTTP using request parameters (for GET requests), with the input
name attribute used to set the parameter "key". So your HTTP request will have the following params: ?iwd0_tax=userInput1&iwd0_discount=userInput2
etc.
Grails makes request parameters available by the params
var in controllers:
def iwd0_tax = params.iwd0_tax
Grails can also populate a bean/class from the request params automatically. The bean is called a command object
. See details in the Grails docs.