"He likes the apple."
Translation:Er mag den Apfel.
The verb changes depending on the person you're talking about. Remnants of this also exist in English: you say "I like" but "he likeS" with an additional "s".
mögen (to like)
ich mag (I like)
du magst (you [sgl., informal] like)
er/sie/es mag (he/she/it likes)
wir mögen (we like)
ihr mögt (you [pl., informal] like)
sie/Sie mögen (they/you [sgl. + pl., formal] like)