Adjectives are words that modify nouns and can be divided into categories describing personality, feelings, appearance, condition, and size. Personality adjectives describe one's character positively as funny or negatively as lazy. Feeling adjectives indicate emotions like happy, sad. Appearance adjectives relate to looks and can be positive like handsome or negative like fat. Condition adjectives refer to one's situation as clever or careful. Size adjectives denote height and width as that dog is taller or that girl is fatter. The document also mentions ordering adjectives and includes exercises.