Airport transit visa
Airport transit visa (VTA)
Airport transit visa is a visa that allows the holder to transit through the international zone of a French airport with no access to the Schengen space, before flying on to the final destination outside the Schengen area.
Special case of a transit through two different airports / terminals in Paris: you are allowed to remain in the international zone, but not to go through Immigration control.
Therefore, if your itineray makes you change airports or terminals or go though Immigration control, you will need to apply for a Schengen Visa.