!By Shadow Fox Vertigo
Well, in Japanese the word "Kitsune" just mean fox.  How exciting eh?  However, there are many many legends about multiple tailed foxes in the Japanese culture.  Spiritual foxes, mystical foxes, etc.

Kitsunes are shape shifters.  They are very good at learning what you like and know how to play on it. They can be very seductive or very frustrating.

!By [http://wuzzle.org/~storm/1583/legends1.html|(Website)]
A kitsune is one of the many kami that inhabit the world, a powerful one, a spirit-fox. Kitsune always have more than one tail, and the more tails, the more powerful the kitsune. A three-tailed kitsune is of little account, but a nine-tailed kistune--nine being the Number of Heaven--a nine-tailed kistune is a fearsome thing indeed.

Kitsune always have two forms. They appear as a fox with many tails, a clever fox red as blood, white as snow, or black as night, sometimes silver as moonlight. And they appear as a human woman of great and dangerous beauty, a beauty that clouds the minds of men and woman alike. A kitsune in human form can only be told from human by their reflection in water--and only running water at that!--where you can see their tails and the fox ears peeking out from beneath their hair. Some say that the only way to tell a kitsune is to cut her head off and see if she reverts to her fox shape, but that is an ugly rumor spread by jealous men. They accuse an innocent woman of being kistune, kill them, and then oh so sorry we were mistaken. Pah!

Kistune are, like their mortal brethren, tricksters. They delight in seducing mortal men and woman, making them fall in love with the woman they appear as, and then tricking them into making great fools of themselves. Some kitsune are kind, and allow their lovers chances to discover their ruses, reasoning that if their mortal is so foolish as to not notice their clues, they deserve their fate. But others are neither kind nor gentle, but have hearts as cold and black as a winter night. These kitsune never take a chance of being discovered, but instead draw their victims into their trap so very gently, maddening them with desire. And when the trap closes, their mortal lovers usually die. 

!By [http://www.angelfire.com/yt/sonicandknux/kitsune.htm|Tails]
Kitsune are called werefoxes by some people. Originally I heard that their power is determined by the amount of tails that they have, but apparently that's not quite true. Their power is actually determined by their age. the older a kitsune is, the more power he/she has. And they don't get old like mundane critters, they just get more powerful as they age. A kitsune can be killed only with jade, but I have no idea just why. It's probably their only weakness or something.

Antoher thing I learned about them is their ability to shape shift. This is one of their powers, designed to hide them whenever needed. A kitsune can appear as a fox or a human, but can also appear as a cross between the two if they so choose. (Personally, I think that in this state they would only have one tail, but don't hold me to that.) They are also very crafty characters, and are very difficult to catch or even see unless one actually lets you, which possibly happened at least a couple of times, since there are legends about them. 

!By Crymsin_vulpes
Kitsune, a sort-of subculture of therian, have many stories behind the magicks or powers they hold. These are the fox-demons that appear most frequently in anime series, and Chinese folklore. They say that a Kitsune is naturally a succibi --the legends usually state that they are female only, though the kitsune race as a whole is not entirely made of females. There are males, but the culture is generally feminine-- this may be true, if you yourself are a Kitsune, or you know any; ask them what they think. In the least, Kitsune tend to be seducers.

In part of the succubi theory, it is stated that the effect of lovemaking for a kitsune's partner is, according to many sources, more pleasurable than most humans can handle. (I think I can relate to this somehow, I seemed to turn a now ex-boyfriend into a nimph...but that's a whole different story.) Sex is a common feeding method used by Kitsunes, for they are also known to be psi (psionic, psychic, perhaps even emotional) vampires.

Even as a vampire, the Kitsune can feed off of many things including: words, knowledge, the land (elements), music, writing, and humans. Through many Chinese folklore stories, a Kitsune is described as a 'punisher' of sorts. The lovers they take may be very undeserving (and unwilling), and do waste away unless a Priest breaks the 'link' between they and the Kitsune. Those deserving (and willing) lovers though, stand a great chance of living happily and healthfully.

The difference between the Kitsune and today's therian were-foxes is that a Kitsune never takes on a anthromorphic form or bipedal form in anyway, they will only go between that of a human or true fox. It is said that a were-fox can feel their 'ears' atop their head, for a kitsune, in contrast, feel them where their human ears are. They twitch, rotate, etc. A lot of kitsunes find themselves highly attracted to Asian culture, being that they are a keen part of Chinese folklore. Others can even 'tell' when a person is kitsune; these people are usually children though, or adults with the heart and 'wide-eyed innocence' of a child. (One comment I've recieved is that I look like a fox: that they've seen my eyes glow, etc.)
Sometimes though, when a Kitsune is in fox-form, it may show more than one tail. This is a 'badge of honor' along with wisedom, it is thought that they gain tails through good deeds and noble acts, other lore states that they gain them with age. The most tails a Kitsune can gain/earn is nine, leaving the Mother of Kitsune with ten tails.

In some theories it is debated whether or not a kitsune-human can choose to take the form of a fox and travel the earth long after their death, that instead of being born a kitsune---they were just magical beings and they fancied a fox-form. It is also said that when the kitsune-human dies, their spirit can possess yet another human body.

Although the fox is generally known to some as a trickster, a Kitsune is known to be a good luck charm and guardian spirit. In lore the Kitsune pledged their allegiance to the God Inari; the god of grain, fields, and rice. In return for their loyalty, the Kitsune could take shelter in his temple. Though when non-Inari Kitsune (nongitsune) turn about toil and chaos amoung the human race, the humans turned to the Kitsune and prayed for their assistance. Although they are to be guardians, the Kitsune is known to randomly annoy humans.

Kitsune magic includes: seduction (which may just be considered mind-control, or powerful charming), possession, illusion, and fox-fire. Fox-fire is the creation of small orbs of fire, self-explanitory.

!Notes to the above by Salem
* Kitsune are not a subculture of Therian, it has no connection with Therianthropy whatsoever. 
* Kitsune as a word is Japanese for fox, I believe you are refering to the Huli Jing (the Chinese Kitsune), there is also a Korean Kitsune called KuMiHo. 
* (Regarding the difference between the Kitsune and today's therian were-foxes) Incorrect, Kitsune have three basic forms... traditional Fox form, a hybrid of a Fox-Human form, and a Human form. Let me say that though there are few similarities of were-foxes and Kitsune, there is no connection between them. They are two completely different races. 
* (Regarding the Mother kitsune) This is correct but it is also said that she has 1,000 or even 10,000 tails according to Korean folklore. 
* Inari (or sometimes refered to as Oinari) is also God/dess of wealth. Yes, Inari is also refered to as a Goddess by some aswell since no one truely knows his/her gender.
* (Regarding "nonginsune") The correct term is "Nogitsune".
* Fox-Fire is called Kitsune-Bi. Shapeshifting is refered to as Henge. Possession is refered to as Kitsune-Tsuki. There are others such as control over certain elements. And Hoshi-no-Tama, an orb used for energy storage.