The category of case of nouns

Definition: A noun is a word that names a person, place, thing, or idea.
Concrete nouns name people, places, or things that you can touch, see, hear, smell, or taste.
Person
Place
Thing
man
river
dog
Mrs. Jones
Paris
book
doctor
mountains
sports car
Maddie
home
Ferrari
Abstract nouns name ideas, concepts, or emotions. These nouns are intangible, which means you cannot touch, see, hear, smell, or taste them using your five senses.
Idea
Emotion
love
happiness
intelligence
anger
justice
excitement
religion
fear⁴

2.2. The theory of “positional” cases.
What is a noun? definition, types examples, exercises with the solution are discussed here. The word which means the name of anything is called a noun. Nouns can also be classified as count nouns or non-count nouns; some can belong to either category. Another category is a concrete and abstract noun. The most common part of the speech; they are called naming words.
Noun definition and classification with their examples are here in discussed in this post very deeply with interesting way.
Noun definition for kids:
The name of anything is called noun.
Noun Definition in a large context:
The word which means any name of a person, material, animals, summations of something, condition, or any quality is called noun.
The noun has the following characteristics:

1. 
   Any member of a class of words that typically
   
2. 
   Can be combined with determiners to serve as the subject of a verb;
   
3. 
   Can be interpreted as singular or plural,
   

4. 
   Can be replaced with a pronoun,
   
5. 
   Refers to an entity, quality, state, action, or concept
   
6. 
   Gerunds are also nouns that are identical to the present participle (-ing form) of a verb, as in “We enjoy swimming more than cycling.”
   

a person (police officer, Michael),
place (coastline, London),
thing (necktie, television),
idea (happiness), or quality (bravery).
An appositive is the renaming or amplification of something earlier in the sentence. In the sentence "Ronald E. Pepin, translator of several Latin texts, will speak at our symposium on translating dead languages tomorrow," the phrase "translator of several Latin texts" is a re-identification of the person's name, an appositive. Occasionally, pronouns can fall into the appositive slot of a sentence and that can create questions about case. If the appositive is renaming something that functions as a subject, the pronoun should take the subject form; if the appositve is renaming something that functions as an object, the pronoun must take the object form.⁵
The two people in charge of the symposium, Micki and I, will help pay for the damages. (where "Micki and I" renames the subject, "two people")
Nobody in the auditorium, not even he, expected that a riot would break out. (where "he" agrees with the subject "nobody")
My favorite professors, Dr. Pepin and she, gave interesting talks. (where "she" corresponds to the subject "professors")
Great Grandmother Etherea left her money to her favorite people, Jayden and me. (where "me" agrees with the object of the preposition "people")
The bank credited two different groups, the Stamp Club and us, with making deposits on the same day. (where "us" agrees with the object "groups")
When a sentence with compounded pronouns sounds intolerably klutzy, the sentence will have to be rewritten. "The group gave certificates of recognition to the two oldest members, him and me" might sound better as "The group gave certificates of recognition to him and me [or 'to both of us'], the two oldest members" or "He and I, the two oldest members of the group, received certificates of recognition."
Occasionally pronouns are connected to other subjects or objects in the sentence. In that case, the case of the pronoun can be important and errors are apt to be made, especially in the object position. Generally, the choice becomes obvious when you drop the noun or noun phrase that the pronoun is combined with.
We students can no longer tolerate the administration's mismanagement of funds. [We can no longer tolerate … ]
The administration has given us students no alternative. [… has given us no alternative.]
In the second person, this is not really a problem, because the form of "you" remains the same whether it is singular or plural, subject or object.
You students need to take care of this situation on your own.⁶