The "Carte Orange" is a pass for public transport (subway, buses, suburban trains).

The card for museums is "Carte Musées et Monuments" (Museum and Monument pass).

You can have details in the Paris Transit authority website at

http://www.ratp.fr/Eng/index.htm

Check the "Travel Guide" area, which gives details on tickets, "Carte Orange", Tourist passes, "Carte Musées et Monuments".