Hi @Gowthamp16682578: Please find the below for better understanding. Though the docs are from earlier version, this still holds good.

Primary page: https://docs-previous.pega.com/sites/default/files/help_v718/definitions/p/primarypage.htm

Parameter page: https://docs-previous.pega.com/sites/default/files/help_v71/definitions/p/parameterpage.htm

In general: Primary page is based on the context for a rule. Properties available in the primary page can be accessed in the rules directly. Parameter pages are class less pages to store temporary parameters (which can also be passed from one rule to another)

Thanks. 

Hi @Gowthamp16682578,

Please see the below suggestion:

Primary :

The primary always refers to the page context under which your current rule is being executed

Parameter:

A parameter page contains parameter names and values. This page has no name or associated class. The stack of parameter pages for the current process is not part of the clipboard and is not visible through the Clipboard tool. However, you can display the contents of the parameter page with the Tracer tool.

Regards,

Mohd Qizer Uddin.