A button that is rendered as an HTML input element with the type attribute set to submit, reset, or
image, depending on the <apex:commandButton> tag’s specified values. The button executes an
action defined by a controller, and then either refreshes the current page, or navigates to a
different page based on the PageReference variable that is returned by the action.

An <apex:commandButton> component must always be a child of an <apex:form> component.
See also: <apex:commandLink>

A.
apex:commandButton

B.
apex:flash

C.
apex:emailPublisher

D.
apex:actionRegion