The word noun comes from Latin nomen, which means name. At a basic level, a noun names a person, place, or thing:
Often you can put an article (the or a) before the noun, a verb afterwards, and before you know it you have a sentence:
The phone rang.
As with all parts of speech, a word’s function in the sentence is dependent on context, on how it interacts with the words around it. With every new part of speech that you learn, the previous ones will come into focus more clearly.