Anoun that tells who or what a sentence is about is a noun.

A noun that tells who or what a sentence is about is a subject noun. The subject in the sentence is the doer or the actor of the verb in the sentence while a noun is a part of speech that can be person, thing, animal, place and even and idea. Some examples of subject nouns are museums, toys, Rina, Cebu City, birthday and a lot more. The subject of a sentence can actually be nouns and pronouns. The pronouns will take the place of a noun such as You, me, it, he, she, we, they and others.