The document discusses count and non-count nouns. It defines a noun as a thing, person, animal or group thereof. Count nouns refer to things that can be counted, like cars or apples, and can be singular or plural. Non-count nouns are things that cannot be counted, like sugar or oil, and are only used in the singular form. While non-count nouns are not pluralized, they can be used in phrases involving count nouns, like "a bag of sugar". The document emphasizes the distinction between count and non-count nouns.