They finally opened the door for him.
In this first example, the verb “opened” is an action verb since it is describing a specific action performed by someone.
The teacher challenged her.
In this second example, the verb “challenged” is also an action verb since it is describing an action.
Linking verbs, on the other hand, do not describe an action but link subject and verb by providing more information about the subject. An example of a linking verb is “The cake smells good”. In this case the verb “smells” is connecting subject and verb.