For many German tenses, the verb itself is locked in a non-varying form of the infinitive or past participle (which normally starts with ge-) that is the same regardless of the subject, and then joined to an auxiliary verb that is conjugated.
For numerous German tenses, the verb retains a constant form from the infinitive or past participle (beginning with ge-) that does not vary based on the subject, and then linked to an auxiliary verb that is conjugated.