In grammar, a preposition refers to a word such as from, to, by, in, to, for, etc. that connect different sections of a sentence such as nouns, pronouns or phrases. On the other hand, a prepositional phrase is a phrase that begins with a preposition and it is followed by words that act as objects of the preposition or describe this object. This means in the case of "Kali worked hard to meet her deadline" that contains the preposition "to" the prepositional phrase is "to meet her deadline" as this contains the preposition of the sentence and the object or wors related to the preposition.
