The words is, am, and are are forms of be verbs.

Examples:

The forest is the old man's favorite place.

I am his special friend.

The trees in the forest are green; the rivers in it are clean.

The words is, am, and are do not show action. They show a state of being. They are called be verbs.

Use the be verb is with a singular noun or pronoun.

Example: The forest is the old man's favorite place.

Use the be verb are with a plural noun or pronoun.

Example: The trees in the forest are green; the rivers in it are clean.

Use the be verb am with the pronoun I.

Example: I am his special friend.