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
Watch out: we don’t use Present Perfect even if there is a recent action with present consequences, when this action took place in the period of time that already finished: yesterday, last week, 1 second ago, a millisecond ago. Also, when time period is not indicated explicitly, however, we can understand that it’s finished from the context. Please, see Present Perfect Usage 0: When we don’t use Present Perfect.
This topic has a very close relation with “recent action”, as recent actions in many cases affect the present situation. Even these two topics are sometimes combined into one by some authors. See “Present Perfect Usage 5: Recent Action” to compare.
More on Present Perfect: