Hi, I'm Heather Kamins for About.com, and I'm here to talk to you about what a verb is.Verbs are often known as action words, and they can describe an action like flying or walking, and they can also describe a state of being like existing or believing.Every complete sentence needs both a verb and a subject, which is the person, place or thing that does the action. So for example: The birds flew south for the winter. In that sentence, birds is the subject, and flew is the verb. You want to make sure your subject and your verb agree in number.Sometimes subject and verb can be separated by prepositional or other phrases. You want to be careful that they still agree. So in this example:The boy, who lives near the woods, runs. You still want to make sure that the boy and runs agree with each other.Thanks for watching. To learn more, visit us on the web at About.com.