There are two types of articles in English grammar e.g. definite and indefinite article. For students this topic is very easy and anyone can gain high score so learn total three articles A, An and The in English Grammar.
An article is a word which is used to modify a noun. It knows special adjectives words a, an, and the are called articles in English.
Indefinite articles are a and an that are used before singular countable nouns beginning with a vowel (a, e, i, o, u) or vowel sound.
Generally define article (The) is used before unique nouns or things which are single or unique (no simillar other object) in the world. like the sun, the moon, the sea etc.
Everywhere can not be used articles (A/AN/The) in English sentences. Some sentence where should not use articles, it is not article sentence. Generally we use it anytime, but its wrong. According examination students have to learn how to build correct sentence with articles or no articles.