Here's why:
* Prepositional phrase: It consists of a preposition ("of") and its object (the phrase following "of").
* Adverb: It modifies a verb, adjective, or another adverb. It tells us how, when, where, or to what extent something is done.
Example:
"Instead of going to the park, we went to the museum."
* "Instead of going" is a prepositional phrase modifying the verb "went".
* It tells us what the speaker did instead of going to the park.
Let me know if you have any other questions!