This isn't an easy topic, but I will keep this as simple as possible.
Hip-Hop started off in New York City in the late 1970's and early 1980's. Hip-Hop was comprised of three different areas. The written word is called Graffiti, the spoken word is called Rapping, and speaking with your body is called Breaking (Break Dancing.) Hip-Hop as a word is lost on today's generation in America and Chinese don't have any better of an understanding. If we want to understand something, we must research it. Luckily, there is a documentary movie that captures the birth of Hip-Hop. The movie is called, 'Style Wars.'

The movie is focused around Graffiti as it is the most visual aspect of Hip-Hop. But you get a taste of breaking and rapping.

You can see the movie here, but there are no subtitles, sorry. Even if you can't understand every word, it's good for your English listening. People from New York City can be hard to understand.

http://v.youku.com/v_show/id_XODQ3NjYxODA=.html

If you watch this movie, you will understand what Hip-Hop means as this movie shows its birth! Enjoy!

More info on Graffiti:
An element of the Hip Hop culture misinterpreted and misrepresented by the mainstream media, and most especially hated by affluent (usually white) businessmen who don't understand the roots or meaning of the writing on the walls.

Contrary to popular belief, Graff is NOT any of the following: writing on houses of worship, people's houses in general, other writer's names, or tombstones. The aforementioned need not be identified with bus, train, subway and wall burners. That's REAL graffiti, the visual aspect of Hip Hop accompanied by the physical (breakdance), verbal (emceeing), and rhythmic (turntablism).

Since Graffiti is an element in Hip Hop just as important as DJing, MCing and Breaking, any assault on Graffiti (i.e., calling it "vandalism", "not art", etc.) should be viewed as an assault on Hip Hop altogether.

From the beginning, the powers that be have sought afte the destruction of our culture, from transit authorities chasing after writers, to housing police harassing people at block parties, to lawsuits being filed against DJs for sampling ("copyrighted" material). Now it may seem like everything is okay since Rap has hit the mainstream, but the major corporations threaten its existence every day. Remember the last Rap video you saw on TV. Did you see any tags, any DJs working the wheels of steel, any B-Boys tearing up the floor, any MCs really rocking the party? Or was it just images of scantily clad females, guys flashing their "bling", and "gangstas" shooting their guns off? Chances are it was the latter, the money-making gimmick that corporations such as MTV make money off of today.

These very same corporations, usually headed by conservative individuals who "care" about their buildings, are the organisations which lobby for tighter anti-graffiti laws. So it may seem that "Hip Hop" is all well with mainstream America, but they're actually destroying us from within, in more than one way.