1) A porte cochère was originally a gateway to a building large enough to permit a coach to be driven through it into an interior courtyard.

2) Later, the term was applied to a portico-like structure built over a driveway at the entrance to a building. Its purpose is to provide shelter from the weather for those getting in or out of a vehicle. Pronunciation here.

Porte cochère. Allison Mansion, Indianapolis, IN. 1914.