What part of the sentence tells what subject is or does?

The part of the sentence that tells what the subject is or does is called the predicate.

Here's a breakdown:

* Subject: The person, place, thing, or idea that the sentence is about.

* Predicate: The part of the sentence that tells us something about the subject.

Example:

* The dog barks loudly.

* Subject: The dog

* Predicate: barks loudly

The predicate tells us what the subject (the dog) does (barks loudly).