It means "what's up?", "I don't understand you, explain it better" or "what's happening?"
it is UK slang but is commonly used by people of all backgrounds.
A phrase, origin of which is in Hebrew and now one of the most popular phrase in Israel. It's equivalent to "stop complaining like a baby" but much more cynical.
it's usually used when someone complains about unimportant things.
She: I'm 40, single, ugly and got fired today.
Me: I hear what you're saying and it sounds like Oy Yoy Yoy! I'm so miserable! No one wants me! I'd rather kill myself!