An adjective modifies a noun or pronoun. In this case, "modifies" means "tells more about." Adjectives are words that describe things.
I planted orange flowers in the round pot.
The long-eared rabbit nibbled the little carrots.
Adjectives can answer the question "What kind?" (orange flowers; little carrots)
A possessive adjective modifies a noun by telling whom it belongs to. It answers the question "Whose?" Possessive adjectives include his, her, its, my, our, their, and your.
You can share my rice.
Have you seen their house?
The demonstrative adjectives that, these, this, those, and what answer the question "Which?"
I'm going to open that present.
Those socks look warm.
A demonstrative adjective may look like a demonstrative pronoun, but it is used differently in the sentence: it is an adjective, used to modify a noun or pronoun.
The interrogative adjectives what and which are used in a question. They help to ask about something.
What movie do you want to see?
Which leaves turn color first?
An interrogative adjective may look like an interrogative pronoun, but it is used differently in the sentence: it is an adjective, used to modify a noun or pronoun.
An indefinite adjective gives indefinite, or general, information. Often, it answers the question "How much?" Some common indefinite adjectives are all, any, each, every, few, many, and some.
Many children like dinosaurs.
Did you want some bananas?
An indefinite adjective may look like an indefinite pronoun, but it is used differently in the sentence: it is an adjective, used to modify a noun or pronoun.
See also: Adjectives: Happy Little Clouds and Adjectives Versus Adverbs.