What does the mean in German?

I´m not sure if I got your question right. If you wanted to know what "the" means in German, heres the answer:
While the English language has just one article ("the") there are three of them in German. You have "Der" for male words, "Die" for female words and "Das" for neutral words. For example you would say "Der Hund" but "Die Blume" while in English you would be using "the" for both words ("the dog", "the flower")
It´s really kind of complicated ´cause without knowing it by learning you can hardly tell what gender aword is. Even the German people sometimes have problems to know the article of a word they do not know.
Answer
I suspect he wanted to know about the umlaut, the two dots over some German vowels.
The umlaut changes u from u as in mutt to oo as in moo
it changes a from a as in mad to e as in med
it changes o from o as in top to er as in tern