In germany, i hear a lot of jokes containing "deine Mudda". I don't understand them, what does this mean, and what kind of jokes are containing them?
Joking viciously about your mother is an indirect way to insult you: if your mother is so bad, you seem to be even worse.
The typical jokes include some negative comparisons of smb's mother with some illustrative example, following the form "`Deine Mudda ist so ... dass sie (sogar) ...". Those comparisons are usually very funny and make the overall joke sound not so dirty or insulting, but rather eliciting some laughing and smiling.
Your mother is so fat that she is sitting while she is standing.
You mother is so fat that when she stands on the scales it shows her cellular phone number.
Your mother is so fat that when she was lying on a beach Greenpeace threw her into the water.
Your mother is so silly that she goes to the left in Mario.
These jokes are also common in English (and probably originate from English language), but are rather limited to the mother being fat. Here are some examples:
In addition to Alexander's answer, I would like to add that simply replying "Deine Mudda!" means something like "Get lost!". Of course, as with all youth slang, usage probably varies highly by region and even social circle.
This is shortened from a form of exchange often seen among adolescents:
This means something along the lines of "Yes, I understand; don't bother me!" (Or "I disagree with your statement"). It is obviously not a nice thing to say, but often used as a form of bantering among friends.
There are some regional variants. In bavaria, for instance, I've heard the variant "Dei' Mudda", which is "Deine Mutter" in bavarian dialect.
"Deine Mudda", pronounced like Hamburg slang, is used nationwide, though, probably popularized by hip-hop artists. There is a big and influential hip-hop scene in Hamburg. Of note, there was a 1999 Single by Hamburg hip-hop stars Fünf Sterne Deluxe named "Ja, ja... deine Mudder" which reached position 38 in the german single charts. The record label was called "Yo Mama Records"...