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.
In many German verb forms, the base stays as either the infinitive or past participle (starting with ge-), which remains unchanged irrespective of the subject, while an auxiliary verb is used and conjugated accordingly.