When you want to pass the Product object directly to a page, start the page with a dataview with datasource context and entity Product. Connect that page directly to the button. Mendix will handle the passing of the object.
But when you want to add the product to a order or shopping basket of a logged in customer, you need a microflow
That microflow should start with a input parameter of type Object and entity Product.
Connect that microflow directly to the button. Mendix will handle the passing of the object into the microflow.
More basics are explained in the following Mendix Academy Learning path; https://academy.mendix.com/link/path/31/Become-a-Rapid-Developer