Both English and German refer to past events using the simple past tense and the present perfect tense. The perfect past tense is called Perfekt in German, but it is important to understand that although the German Perfekt is considered the closest equivalent of present perfect in English in terms of its structure, in fact there are some notable differences in the ways each language uses this tense.
Both English present perfect and German Perfekt have in common that they are compound tenses, formed with an auxiliary or helping verb together with the past participle. This auxiliary verb is usually "to have" (haben) and sometimes, in German, "to be" (sein):
Wir haben sieben Tafeln Schokolade gegessen.
We have eaten seven chocolate bars.
Caption 15, Konjugation: Das Verb „essen“
Wir sind zusammen in die Stadt gegangen.
We have gone to the city together.
Caption 12, Konjugation: Das Verb „gehen“
The main difference, however, is that the English present perfect refers to an action or state that begins in the past and continues into the present, whereas the German Perfekt is usually used to speak about completed states and actions, and is therefore rather the direct equivalent of the simple past tense. In fact, Perfekt is often called the "conversational past" because it is the primary spoken form of the past tense. In many cases where spoken English would use the simple past tense ("We already ate."), German would almost always use the Perfekt tense (Wir haben schon gegessen).
Alternately, the German Präsenz (present tense) can sometimes be best translated into the English present perfect:
Und Gitarre spielt die Vierunddreißigjährige schon seit ihrem sechsten Lebensjahr.
And the thirty-four year old has played guitar since her sixth year of age.
Caption 12, Ann Doka & Band: New Country aus dem Rhein-Main-Gebiet
Read this article about simple past vs. Perfekt and take this quiz about the German Perfekt tense, then find some examples of the tense used in real conversations on Yabla German.