In order to form the German Perfekt (past perfect) tense, which is the most common past tense used in German colloquial speech, you need to combine a helping verb (auxiliary verb) with the past participle form of the verb you ultimately want to conjugate.
German dictionary form: essen
Perfekt (1st person singular): ich habe (auxiliary verb) gegessen (past participle of "essen")
Every time you form the Perfekt, you need to choose between "haben" and "sein" as your auxiliary verb depending on the verb you conjugate.
As a rule of thumb, the vast majority of action verbs are combined with the auxiliary verb "haben", whereas most verbs describing either state or directional movement are combined with "sein".
to make / zu machen (action verb)
haben + past participle of "machen"
==> ich habe gemacht
to go / zu gehen (verb describing movement)
sein + past participle of "gehen"
==> ich bin gegangen
to be / zu sein (verb describing state)
sein + past participle of "sein"
==> ich bin gewesen
Check out this grammar quiz below to test your knowledge on the German Perfekt form!