Having an irrational or unexplained preoccupation or preference for some object, in order to gain sexual arousal.
While not strictly an addiction, it can be similar in that one has a very irrational or fixated presence. A lust for boys with blond hair is a fetish, or the unexplained desire to be tied up and be humiliated is another. The desire to only suck cocks that are uncut or if a person is wearing a brown sock is a fetish.
In Porn, many of the Niches are derived from satisfying a specific fetish or fixation. Redheads only that are Twinks would be a niche, but also a fetish.
Niche is more about the category, while fetish refers to the desire itself, the insatiable need for that very specific satisfaction. Redhead Twinks would mean that one couldn't be fully satisfied if the person wasn't a redhead and a Twink.
There are some who refer to having a fetish as also having an obsession for a body part, feature, or inanimate object, such as a dildo for example.
More generally used to describe some form of sexual behavior not considered within the mainstream categories. A foot fetish or latex fetish are examples.
Alfred Binet introduced the word as a psychological meaning for the sexual admiration of an object, in 1887.The meaning was further expanded in 1912, thanks to studies by the heavy weights in the shrink business, such as Freud. At the beginning it was considered an 'illness' and only after the Kinsey Report did the concept of 'fetishism' gradually cease to be considered an illness. Much like how at first these groups considered Homosexuality a disease.
History (Modern): Today's opinion is that fetishism is more accepted, is actually a normal reaction to sexual stimuli. There are still some guidelines that will class a person's fetishism as being an illness, requiring treatment, but is no longer as encompassing as it used to be.
Furies is a fetish. This is where a person needs to dress up like a furies animal, in order to become sexually aroused.
Foot fetish is about an obsession with the feet, whether its size, color, or shape.
The bottom line is that a person becomes sexually aroused only if certain body parts are shaped or formed a certain way, or if specific inanimate objects are used.
Practice (Associated Acts): Preference for a sexual act is not necessarily a fetish. The criteria requires an unusual obsession with the act, where it is vital for that person to achieve sexual gratification.
A person who requires to be tied up, humiliated, or treated roughly in order to become sexually aroused, and finds other forms unsatisfactory, would be a fetish.
Noteworthy: Some of what is termed as an illness, includes a heterosexual male's fascination for woman's clothing, such as lingerie. There are medications that can be used, that reduce the person's sexual desire, thus supposedly eliminating the fetish craving. In addition, surgery can be a method of altering a person's fetish cravings.
Other 'treatments' include role playing, aversion therapy and other technical terms. All are designed to either reduce the craving, fetish, or to stop it. This assumes that the fetish itself, is not a normal sexual desire. A conflict with modern thoughts on it.
Religious or Legal Fetishism are similar. Religious Fetishism for example place spiritual quality to inanimate objects.
Legal Fetishism is where one actually believes they exist because of the law.