There are two articles in English language: "the" and "a/an". Article are used for nouns.
An article, like an adjective, modifies the noun. It adds to meaning of the noun. An article is always used before a noun or an adjective that modifies the noun.
Examples:
Articles are divided into following two types:
a. Indefinite Article: ("a or an")
b. Definite Article: ("the")
The indefinite article "(a/an)" is used for common (non-specific) nouns.
Example: He bought a shirt.
In above example. the "shirt" is a common noun. The noun "shirt" refers to a group of common things. It can be any shirt. It is not specific or any particular shirt.
On other hand, the article "the" is only used for a specific or a particular noun.
The article "the" must be used before particular nouns such as the job, the holy book.
The article "the" may also be used before a common noun, if the common noun is intentionally used as a particular noun in some context.
Example: He won the competition.
Other Topics: