Adjectives are words that modify nouns. They describe nouns by telling us the color, age, size, or some other characteristic of that noun. Unlike adjectives in some languages, in English they have a single form - they do not change according to gender, number, or location in the sentence.
Demonstrative adjectives indicate which thing or group of things you are talking about. In English, there are four forms according to the number of items and where they are located in relation to the speaker.