http://en.wikipedia.org/wiki/Japanese_titles
Kun
Kun (ŒN, Kun?) is an informal and intimate honorific primarily used towards males (It is still used towards females, but rarely.) It is used by persons of senior status in addressing those of junior status, by males of roughly the same age and status when addressing each other, and by anyone in addressing male children. In business settings, women, particularly young women, may also be addressed as kun by older males of senior status. It is sometimes used towards male pets as well.
Schoolteachers typically address male students using kun, while female students are addressed as san or chan. The use of kun to address male children is similar to the use of san when addressing adults. In other words, not using kun would be considered rude in most situations, but, like san for members of one’s own family, kun is traditionally not used when addressing one’s own son (unless kun is part of a nickname: “Akira-kun”—Akkun) or when referring to one’s own child in conversations with others.
In the Diet of Japan, diet members and ministers are called kun by the chairpersons. For example, Jun’ichirō Koizumi is called “Koizumi Jun’ichirō-kun”. The only exception was that when Takako Doi was the chairperson of the lower house, she used the san title.
Chan
Chan (¬Ç¬ø¬Ç√°¬Ç√±, Chan?) is the hypocoristic suffix, used to refer to children, animals, and people whom one has known since they were children. To use chan for adults whom one has not known since their childhood requires considerable intimacy, less for women than for men. Furthermore, attaching chan to a modified stem is more intimate than attaching it to the full form of the basic name. Chan may also used for celebrities as a title of affection. For example, Arnold Schwarzenegger gained the nickname Shuwa chan in Japanese. Although traditionally honorifics are not applied to oneself, some young women occasionally develop the habit of referring to themselves in the third person using chan. For example, a young woman named Maki might call herself Maki-chan rather than using a first person pronoun. Chan is also used for pets’ names and when referring to animals, such as usagi-chan (or, more frequently, usa-chan: rabbit+chan) (e.g. Tama-chan, the flying turtle in Love Hina), or when speaking to small children.
Non-standard variations of chan include chin (‚¿‚ñ, chin?), and tan (‚½‚ñ, tan?). This last is also the popular suffix for moé anthropomorphisms, which are artistic memes on Japanese imageboards wherein a female character, usually in a kind of cosplay, is drawn to represent an inanimate object or popular consumer product. Part of the humor of this personification comes from the personality ascribed to the character (often satirical) and the sheer arbitrariness of identifying a variety of machines, objects, and even physical places as cute.
Famous examples include the OS-tan (representing computer operating systems) and Bisuke-tan (representing KFC biscuits). Some characters such as Binchō-tan are actual mascots of companies.
The Japanese media use chan when mentioning pre-elementary school children and sometimes elementary-school girls
