What's up?

"What's Up" is an idiom.
An idiom is a phrase that has a different meaning than the words in it.
You cannot understand an idiom by knowing each word in it.
You must understand it as a whole-- as a phrase.

Native speakers use hundreds of idioms everyday.
We don't even think about it.

To understand a native speaker, you absolutely MUST learn idioms.

**How Will You Learn Idioms?

Unfortunately, you don't learn idioms from textbooks or schools. But you can learn them.

To start, buy a Dictionary of American Idioms.
Use it to understand idioms you hear in movies and conversations.
Keep these new idioms in a notebook, and review them quickly everyday.

Movies are great for learning idioms. In fact, many of our most common idioms come from movies.

Thanks to A.J. Hoge
http://www.EffortlessEnglishClub.com