There are two groups of verbs in German:
Strong verbs are called strong because they do not weakly follow the pattern of other verbs. They are more independent.
This is what they do:
If gehen (to go) is identical to weak verbs in the present tense, how would you write out different forms?
stem: geh-
If trinken (to drink) is identical to weak verbs in the present tense, how would you write out different forms?
stem: trink-