1. Texas is not listed in origin state, what does this mean? 2. What is an international driving permit and where do we get it?
You must be referring to the extra insurance you can take out online during the booking process. Below were it says " Rental Car Excess Insurance " you will see in small text " select your state of residence ". Click on this and a drop down list will be displayed. Certain states such as Texas are not included. Texas residents can buy extra insurance protection at the desk on arrival.
An IDP or IDL (international driving permit/license) is basically a translation of your current driving license, it is not mandatory in Europe providing your license is written in English.