When looking at words and how they are used in sentences, sometimes the same word can be used as different parts of speech in different sentences. Words that are usually nouns or pronouns sometimes act as adjectives.
Nouns: Sometimes nouns are used as adjectives.
Rachelle prefers chocolate cookies.
Chocolate is usually a noun, but here it tells what kind of cookies.
That tree branch fell through my kitchen window.
Tree and kitchen are usually nouns, but here they tell what kind of branch and window.
Possessive Nouns: Possessive nouns actually always act as adjectives.
The teacher's desk is in front of the class.
Teacher is a noun, but the possessive form is telling whose desk.
Proper Nouns: Sometimes proper nouns are used as adjectives.
Her dress was covered in Brussels lace.
Brussels is a city, but here it is telling what kind of lace.
That is Maia's new laptop.
Maia is a proper noun, but the possessive form is telling whose laptop.
Proper Adjectives: Sometimes new adjectives are formed from proper nouns. Just like proper nouns, proper adjectives need to be capitalized.
Strangely the Chinese restaurant also served spaghetti, an Italian dish.
China and Italy are places. They become Chinese and Italian when they are used as adjectives.
Pronouns: Some pronouns can be used as adjectives. If a pronoun is used by itself, it is a pronoun. If it modifies a noun, it is being used as an adjective.
These toys are for the children's shelter.
My brother has lost his skateboard.
Which car belongs to your sister?
Some people like warm weather.
This is your sundae. (This what? nothing - it is a pronoun.)
This sundae is yours. (This what? sundae - it is an adjective)