Here's a breakdown:
* Subject: The part of a sentence that performs the action or is described by the verb. It is essential for a complete sentence.
* Noun: A word that names a person, place, thing, or idea.
* Pronoun: A word that replaces a noun.
Examples:
* The dog barked loudly. (The dog is the subject, a noun phrase)
* She went to the store. (She is the subject, a pronoun)
* My favorite book is on the shelf. (My favorite book is the subject, a noun phrase)
Without a subject, a sentence would be incomplete and grammatically incorrect.