Here's why:
* Nouns name people, places, things, or ideas (e.g., dog, park, book, happiness).
* Adverbs describe verbs, adjectives, or other adverbs, often answering questions like "how," "when," "where," or "to what extent" (e.g., quickly, yesterday, here, very).
In the sentence "She waited anxiously," "anxiously" describes how she waited.