i want to know the importance of articles in english language
(Not a teacher)
Articles are quite important in English as they provide certain information about the noun they preceed. Absence or misuse of an article will make a sentence look/sound very strange to an English speaker.
Consider this "sentence":
Dog ate my shoe.
Although the meaning of this is clear, it is ungrammatical in English because it lacks an article.
The determinate article "the" specifies, characterizes, and identifies a noun, and often suggests the listener is already familiar with it. "The" is also used to delimit- to define a certain subgroup. It is also used with geographical sites (but not names of countries unless there is a noun in the name):
The Italian people (not necessarily all Italians but Italians as a group)
That is the most important thing you've ever said.
The cheese I like best is Swiss cheese.
The dog ate my shoe (implies a dog you are familiar with)
The North Sea
The Republic of South Africa (but: South Africa)
If no article is used (if grammatically possible), the noun becomes more general; nouns are often used in the plural in this case,
Milk is full of calcium.
Firearms can be dangerous if they are used by children.
The indefinite articles "a" and "an" also treat a noun in the general sense and are also used to state one's profession:
A dog ate my shoe (implies an unfamiliar dog)
The shots came from a car of unknown type.
I'm a dentist and she's an optician.
Sometimes the article makes little difference in meaning:
The British people love tea.
British people love tea.
Often "the" and "a" are used in the same sentence:
The lion was captured today and it is an individual exceeding two meters in length.
Please consult the web for detailed discussions of the use of articles in English, use of "a" versus "an," and many examples of correct/incorrect usage.