Here's why:
* Adverbs modify verbs: They tell us how, when, where, or to what extent an action is performed. For example: "The dog quickly ran." ("Quickly" modifies the verb "ran").
* Adjectives modify nouns: They describe the qualities or characteristics of a noun. For example: "The red car." ("Red" modifies the noun "car").
To identify adverbs and adjectives, you need to know what word they are modifying. The verb is the key to finding the adverbs, and the nouns are the key to finding the adjectives.