Definition: Adjectives are words that modify nouns.
Like adverbs, adjectives can be single words or phrases. I could say “I live in a brown house.” The adjective is “brown.” I could add an adjectival phrase which adds more information about the house: “I live in a brown house on a curving street across from the sea.” The whole phrase “…on a curving street across from the sea” is an adjectival phrase providing more information about the house.
Now here’s a question I get a lot: “I am good” or “I am well.” It’s confusing because the word “well” has two meanings. One is as an adjective, describing how an action is performed. “He writes well.” It also is a state of health. The rule is that you should use an adjective to modify the subject after a linking verb. That means use “well.” But you could also say “My health is good.” On the other hand, if you are six years old and you want to tell about your behavior to Grandma, you can say “I am good.”