An adjective is a word used to describe a noun or a pronoun.
An adjective gives more information about a noun or a pronoun.
Examples: Raghav is clever. The word clever describes the noun Raghav.
He is also brave. The word brave describes the pronoun he.
Diana is intelligent. The word intelligent describes Diana.
She is also bold. The word bold describes the pronoun she.
Words like clever, brave, tall, short, happy, quick, slow are adjectives as these words give more information about a noun or a pronoun.