In English grammar, the adjective modifies the noun or pronoun using descriptive words.  In most cases, the adjective comes right before the noun in the sentence:

The ugly truck sat in her driveway.

Many people were there.

It was a small party, but it was fun.

An adjective can additionally by modified by an adverb, clause, or a phrase which functions as an adverb.

She admired the carefully painted mugs.

Here, the adverb "carefully" is modifying the adjective "painted".

This article will cover the following forms of adjectives:  Indefinite Adjectives, Possessive Adjectives, Interrogative Adjectives, and Demonstrative Adjectives.

Indefinite Adjectives

Indefinite adjectives, similar to the indefinite pronoun, modifies the noun phrase, noun, or pronoun.

Many cats will chase mice.

Here, "many" is used as an indefinite adjective which is modifying the noun "cats".  In addition, "Many cats" is the noun phrase and the subject of this sentence.

Here are some more examples:

She cooked a few pancakes for breakfast, and they were delicious.

You may come over any time.

Possessive Adjectives

This type of adjective includes "My", "Your", "His", "Her", "It", etc and is very similar to the possessive pronoun.  The only difference is it is an adjective which modifies a noun phrase or noun.

Hey, that's my dog!

Here, "my" is modifying "dog" and "my dog" is the noun phrase and subject. Here are some more examples:

We lost our way.

The bird flew into its nest.

Interrogative Adjectives

The interrogative adjective uses words such as "What" and "Which" to modify a noun or noun phrase.  It is similar to the interrogative pronoun.

Which dog is your's?

"Which" is modifying "dog" while "which dog" is the noun phrase which is also the subject. Here are some more examples:

What time is it?

Which shirt are you wearing?

Demonstrative Adjectives

This type of adjective is similar to the demonstrative pronoun, however, it uses adjectives such as "This", "That", "These", etc. to modify the noun or noun phrase.

When will that book be here?

Here, "that" modifies "book" while "that book" is both the noun phrase and the subject. See more examples:

This kitchen is very cold.

I hope these pants will fit.