What is a Clause?
A clause is a group of words with a subject and a verb that are normally used to add more detail to the noun in a sentence.
A subject is a noun or a pronoun in the sentence, while the verb is the action. A clause conveys information about what that subject is or is doing.
Examples
The shiny, blue car raced around the track.
As a Clause expresses an action or a state of being, a clause can often, but not always, function as an independent sentence.