Learn French: La voiture est parfaite.

Because it describes la voiture (the car), which is a feminine noun. In French, regular adjectives add an e to match feminine nouns. If we were describing a masculine noun, we would use the masculine form parfait without the e.

Does the extra e on parfaite change how the word is pronounced?

Yes, it makes a big difference! In the masculine form parfait, the final t is silent. But in the feminine parfaite, the added e means the t is no longer the last letter, so you must pronounce it.

How can I tell that voiture is feminine?

The most obvious clue in this sentence is la, which is the feminine word for "the". As a helpful spelling trick for the future, almost all French nouns that end in -ure are feminine.

Does the adjective still need to match the noun if they are separated by est?

Yes! Even though est (is) sits between la voiture and parfaite, the adjective is still describing the car. It must be feminine to match the noun's gender, no matter where it sits in the sentence.