A noun is essentially a label for places, things, events, ideas, concepts and so on.
Common nouns are the generic term for something. Common nouns in Spanish are never spelled with a capital letter unless they begin a sentence. Proper nouns are specific names (for example people, cities, or states) and begin with capital letters.
Another way of classifying nouns is according to whether or not they can be counted. Count nouns identify individual entities that can be counted, like siblings. mass noun refers to an entity as an uncountable unit. Mass nouns can be modified with adjectives that refer to quantity, such as mucho or poco since they can not be modified with numbers.
All nouns in Spanish and English are marked for number: singular (one) or plural (more than one). Spanish, like English, usually indicates plurality by adding an -s to the end of the singular noun. Count nouns have both singular and plural forms.
Gender – In English, grammatical gender is based on biology and is relevant for pronouns (he, she, it). Gender in Spanish affects all nouns, pronouns, adjectives and determiners. All nouns have a gender, which determines the gender of any adjectives or determiners that modify it. Spanish genders fall into either masculine or feminine nouns. However, The terms masculine and feminine really mean nothing more than noun class A and noun class B.
Quick Tip! words ending in -aje, -mento, -miento, -ismo are masculine and those ending in -ción, -sión, -ad, -ancia, -encia, -eza, -ía, -ia, -ura are feminine.

Number (Singular and Plural)
In Spanish, a noun is always either singular or plural.
In Spanish the plural is formed by adding an -s to the singular form of the noun for words ending in a vowel: a, e, i, o, and u, or by adding –es to the singular form of the noun for words ending in a consonant or a stressed vowel.
Nouns ending in -s do not change in the plural.
Nouns ending in -z, the plural is formed by adding –es as for other words ending in a consonant, but additionally the –z changes to –c resulting in a –ces ending.