Here's why:
* Adverbial clauses function as adverbs, providing information about how, when, where, why, or to what extent something happens.
* They often begin with subordinating conjunctions like *because, since, although, while, if, when, before, after, unless, until, etc.*
* They modify the main verb of the sentence.
Example:
* When the sun sets, the sky turns a beautiful shade of orange. (The adverbial clause "when the sun sets" modifies the verb "turns" by telling us when the sky changes color.)
Let me know if you'd like more examples or explanations!