Answer:
Since adjectives only modify nouns, and the question to identify nouns is "What is it?", then the only answer the adjective's function answers is "How is it?" as in what carachteristics the noun has. The adjective will not answer the questions: "What does it - the noun- do?" (for verbs), "How does it- the noun- do it?" (for adverbs). So, for instance, if you have the sentence "The bright sun shines warmly".
What is it?: The sun
How is it?: bright
What does it do?: shines
How does it do it?: warmly
