We use an adjective to describe the qualities of people, things, places, etc.
Can you see the young woman at the end of the street?
He's a great singer.
We use an adjective (not an adverb) after 'linking' verbs such as be, become, feel, seem, smell, sound, look, etc.
It looks interesting.
It tastes delicious.
His ideas are interesting.
We can use an adjective to describe the object of a sentence.
His answer made his boss angry.