Articles are used in front of Nouns.

"A" or "An" are always singular.

"The" is singular or plural.

Some plural nouns don't use an article.

When using articles, it's important to also know the difference between count and noncount nouns.

I have glasses.

(plural - a /an )

Or....I have a pair of glasses

You have a hat.

(singular count noun)

But....the second time you describe the hat, you say:

The hat is blue.

He has some strawberries.

(plural count noun)

The strawberries are in his mouth (second mention).

She has a popsicle.

(singular count noun)

The popsicle tastes good!

or....

Popsicles taste good.

The cat has some water.

(Water is a non-count noun)

a / an )

We have time to learn English.

(time and English are noncount nouns. Sometimes the is used; sometimes it isn't.)

They have a good relationship.

(relationship is a singular count noun)

All three children have popsicles.

The popsicles taste good.

(Popsicle is a plural count noun)