The Present Perfect Tense is used when an action completed in the past has a relation with the present.
I have lost my job. An action in the past, such as loosing a job affects the present: no job now.
Other ways to explain:
a past event that has present consequences
there is a connection with now
This topic has a very close relation with “recent action”, even it may be the same rule, click “Present Perfect: Recent Action” to compare.