Nouns are words used to identify people, places, things, or ideas. They serve as the names for objects, concepts, or entities, allowing us to refer to them in language. Nouns can be concrete (tangible objects like "table" or "cat") or abstract (intangible concepts like "love" or "freedom"). They can also be categorized into common nouns (general names for things like "book" or "city") and proper nouns (specific names for particular entities like "New York" or "John"). Nouns can function as subjects, objects, or complements in sentences, playing a crucial role in conveying meaning and facilitating communication.