There are two main types of nouns: common nouns and proper nouns. Common nouns are general words for people, places, and things like "table", "dog", and "library". Proper nouns name specific people, places, and things and are always capitalized, such as days of the week, months, and names of individuals. The document provides examples of common and proper nouns and discusses how nouns can be made plural through different suffixes like -s, -es, or by changing the internal vowel.