Nouns and adjectives are important parts of speech. While nouns help us to name persons, things, objects, places and other concrete things, as well as give shape to abstract ideas, adjectives help us to qualify the nouns and impart more meaning to the nouns they qualify.
The sentence ‘That is his CAR’ tells us that the car belongs to him. CAR is a noun.
The sentence ‘There is DIRT on the car’ gives us more information. DIRT is also a noun.
The sentence ‘That is his DIRTY Car' gives us the same information. Here the word DIRTY tells something more than the first sentence and we form opinions about the car and the person. DIRTY is an adjective which is derived from the word DIRT.