The Perfekt tense occurs mainly in the spoken language. It expresses a past activity.
Usage: Perfect time is typical for spoken language, for conversations, dialogues. The second past tense, Präteritum, is the time of descriptions and stories, typical of the written language. However, the verbs sein, haben and modal verbs (i.e. können, dürfen, wollen, sollen, müssen, mögen) as well as wissen are used much more often in Präteritum, also in spoken language.Formation of Perfekt:
For transitive verbs (with Akkusativ, eg. to like someone/something) and reflexive verbs(z sich, np. sich treffen):
habe, hast, hat, haben, habt, haben + Partizip II.
For intransitive verbs:
denoting movement or change of state, and the verbs sein, werden, bleiben:
bin, bist, ist, sind, seid, sind + Partizip II.
For other intransitive verbs:
habe, hast, hat, haben, habt, haben + Partizip II.
The construction of Partizip II is a separate issue, and is discussed at Partizip II