"Is" and "are" are both forms of the verb "to be" and are used to describe or identify people, things, or situations. Understanding when to use "is" and when to use "are" depends on the subject of the sentence.

Here's a breakdown of how "is" and "are" are used:

"Is" is used with singular subjects:

Examples: He is happy. The car is blue. The sun is shining.

"Are" is used with plural subjects:

Examples: They are playing. The dogs are barking. The books are on the shelf.

To determine whether to use "is" or "are," look at the subject of the sentence. If the subject is a single person, thing, or entity, use "is." If the subject is multiple people, things, or entities, use "are."

It's important to note that "is" and "are" are also used in questions and negative sentences. 

For Example:

Questions: Is she coming? Are they ready?

Negative sentences: He is not here. They are not listening.

Remember, practice is key to mastering grammar. Engage in exercises and activities that involve creating sentences using "is" and "are" to reinforce your understanding.

Keep in mind that this introduction provides a general understanding of "is" and "are" usage. As you delve deeper into grammar, you will encounter more complex rules and exceptions.