The English Present Perfect tense is used to express actions which have already been completed, or perfected, at the time of speaking or writing. In the examples given below, the verbs in the Present Perfect tense are underlined.
e.g. I have done the work.
She has answered half the questions.
In the first example, the use of the Present Perfect tense emphasizes the fact that, at the time of speaking or writing, the work has already been completed. In the second example, the use of the Present Perfect indicates that, at the time of speaking or writing, half the questions have been answered.