Since France and Germany are both in the Schengen zone there is no immigration between Paris and Frankfurt. Once you get to Frankfurt you will be leaving from a different set of gates that are known as non-Schengen. You will have passport control in Frankfurt as you are leaving the Schengen zone.
I like FRA airport. It is big and messy but lots of shops and fun places. You need to walk a lot between areas so make sure you have enough time.
When you check in for your flight in Paris make sure you get both boarding passes and also make sure your luggage is checked through to Amman