There are dynamic and stative verbs in English. Stative verbs describe states that last over a period of time and are not used in continuous tenses. Some verbs like BE, HAVE, and THINK can be both stative and dynamic depending on their meaning in a sentence. The present perfect is used to express something that happened before now at an unspecified time, while the present perfect progressive expresses the duration of an activity that began in the past and continues to the present.