This is the 419th most frequent French word.
vite
Quickly; fast.
In this sentence, 'vite' functions as an adverb, indicating the manner in which the subject walks.
Il marche vite pour ne pas être en retard.
He walks quickly to not be late.
Here 'vite' is used as an adverb to describe the speed of the action of learning.
Elle a appris à parler français très vite.
She learned to speak French very quickly.
In this example, 'vite' acts as an interjection or exclamation urging someone to act swiftly.