The words that we use can be divided into different classes that are called Parts of Speech.
A part of speech is a category of words (or, more generally, of lexical items) which have similar grammatical properties. Words that are assigned to the same part of speech generally display similar behavior in terms of syntax – they play similar roles within the grammatical structure of sentences – and sometimes in terms of morphology, in that they undergo inflection for similar properties. Commonly listed English parts of speech are noun, verb, adjective, adverb, pronoun, preposition, conjunction, interjection, and sometimes article or determiner.
A NOUN
A noun is often defined as a word which names a person, place or thing. Here are some examples of nouns: boy, river, friend, Mexico, triangle, day, school, truth, university, idea, John F. Kennedy, movie, aunt, vacation, eye, dream, flag, teacher, class, grammar. John is a noun because it is the name of a person; Mexico is a noun because it is the name of a place; and boy is a noun because it is the name of a thing. Noun has different forms and functions.
Types of Noun Forms and Functions:
Abstract Noun and Concrete Noun
Abstract Noun: A noun (such as courage or freedom) that names an idea, event, quality, or concept. (e.g Love is an irresistible desire to be irresistibly desired)
Concrete Noun: A noun (such as chicken or egg) that names a material or tangible object or phenomenon–something recognizable through the senses.(e.g A little baby sleeping in a cot)
Note: an abstract noun refers to an action, concept, event, quality, or state (love, conversation), whereas a concrete noun refers to a touchable, observable person or thing (child, tree)
Animate Noun and Inanimate Noun
Animate Noun: A category of noun, referring to a person, animal, or other creature. (e.g The European hunted for presents for his wife and the women on his staff back home)
Inanimate Noun: A semantic category of noun that refers to a place, thing, or idea–not a person, animal, or other creature. (e.g Boluwatife loves to shop. On a March day in an elegant crafts store in Lima, the Peruvian capital, he hunted for presents for his wife and the women on his staff backhome. He had given a speech at a university earlier and just came from a ceremony kicking off a program to help impoverished Peruvians. Now he was eyeing a necklace with a green stone amulet.)
Attributive Noun: A noun that modifies another noun and functions as an adjective.(e.g King Tutankhamun is known as the “boy king” because he became the pharaoh of Egypt at the age of nine) Boy in this sentence is modifying the noun king.
Collective Noun: A noun (such as team, committee, or family) that refers to a group of individuals. (e.g The minority is sometimes right; the majority always wrong, A group of crows is called a murder)
Common Noun and Proper Noun
Common Noun: A noun that’s not the name of any particular person, place, or thing. A common noun represents one or all of the members of a class, and it can be preceded by the definite article (the).(e.g The tree has been stripped of its leaves during the winter)
Proper Noun: A noun belonging to the class of words used as names for unique individuals, events, or places. Contrast with common noun.(e.g Fred, New York, Mars, Coca Cola)
Countable Noun and Uncountable Noun
Countable Noun: A noun that refers to an object or idea that can form a plural or occur in a noun phrase with an indefinite article or with numerals.(e.g The creation of a thousand forests is in one acorn)
Uncountable Noun: A noun (such as advice, bread, knowledge, luck, spaghetti, and work) that names things that in English cannot usually be counted.
Many nouns have both countable and non-countable uses, such as the countable “dozen eggs” and the non-countable “egg on his face.”
Denominal Noun: A noun that is formed from another noun, usually by adding a suffix–such as villager (from village), New Yorker (from New York), booklet (from book), limeade (from lime),lectureship (from lecture), and librarian (from library).
Deverbal and Verbal Noun
Deverbal Noun: A word (usually a noun or an adjective) that is derived from a verb. Also called derivative noun and derivative adjective. Put another way, a deverbal is a verb that has been converted to a noun or an adjective by the addition of an appropriate morpheme. (e.g . . . baker, a noun derived from a verb by attaching the suffix -er.)
Verbal Noun: A noun that is derived from a verb (usually by adding the suffix -ing) and that exhibits the ordinary properties of a noun.(e.g The building with a blue roof.)
Plurale Tantum: A noun that appears only in the plural and does not have a singular form. Plural, pluralia tantum. (A noun that appears only in the singular form–such as dirt–is known as singulare tantum.)
Source: About.com and Wikipedia