Here's why:
* Adverbs modify verbs, adjectives, or other adverbs, providing information about time, place, manner, or degree.
* "Where" indicates location or position.
* Example: "Where did you go?" In this sentence, "where" tells us the location of the action (going).
However, "where" can also be a pronoun in certain cases, functioning as a subject or object of the verb.
* Example: "Where is my phone?" Here, "where" refers to the location and acts as the subject of the verb "is."
So, while "where" is usually an adverb when starting a sentence, it's crucial to analyze the sentence structure to determine its exact function.