Here's what you might be referring to:
* A sentence with a noun as the subject: This is the most common type of sentence. The subject is the person, place, thing, or idea that the sentence is about. It typically comes before the verb in a sentence.
Example: The dog barked loudly. (The noun "dog" is the subject)
* A noun phrase as the subject: This is also very common. A noun phrase is a group of words that functions as a noun.
Example: The big, brown dog barked loudly. (The noun phrase "the big, brown dog" is the subject)
In short, every sentence has a subject, and that subject will either be a single noun or a noun phrase.
Let me know if you had a specific example in mind, or if you were looking for something else. I'd be happy to help clarify!