What does "Jianghu" mean in "People can't help themselves in Jianghu"? What does it stand for?

Jianghu has many meanings in China culture, but most of them represent an ideology and lifestyle other than the official ideology and lifestyle ("temple" or imperial court).

In Hong Kong, it can be called the underworld circle. The Hong Kong film Jianghu is a work about underworld in 2004 (see Jianghu (Movie)).

In many China literature, especially martial arts novels, Jianghu is a chivalrous man, that is, the scope of Wulin's activities. For example, the legendary swordsman by Jin Yong, a famous martial arts novelist, and Hot Blood Online, an online martial arts game.

References:

http://zh.wikipedia.org/wiki/%E6%B 1%9F%E6%B9%96