A geisha is a traditional Japanese entertainer of men. She is a master of traditional arts including music, serving tea (which is a fine Japanese art), dancing and singing etc. Most geisha live in Tokyo or Kyoto (those in Kyoto call themselves geiko. Although in the past it could be argued that geisha were prostitutes (which would be an egregious oversimplification...today it can be easily and accurately said that geisha are certainly not prostitutes.
Geisha have very powerful connections all over the world, hence they are a power to be reckoned with.