Would you think that it was odd if you were flirting with someone and before you had ever kissed, the person asked to touch your feet? If that were to happen, you could probably assume that the person has a fetish. A fetish is an attraction to a non-sexual object of body part that arouses one in a sexual way.
When a body part is fetishized, the person feels more aroused by that seemingly non-sexual part than he or she would from a typical sexual body part. It's easy to imagine a man who has a breast fetish-that is, a man who needs to touch or kiss or breast in order to achieve orgasm. Now stretch your mind a little, and you can probably imagine a person who has a foot fetish-who needs to touch or lick or suck or kiss a foot in order to soar to orgasmic heights.
For many people, an object can become a fetish accidentally in childhood. For example, if an 11 year old boy sees a woman undressing for the very first time in his life, and she is taking off a red silk tank top, then it's possible that for the rest of his life, he will be aroused when he sees a red tank top.
Sometimes fetishes develop during the teen years and are often associated with a person's first sexual experiences. Maybe the smell of leather makes a girl's nipples stand at attention because her first boyfriend was wearing a bomber jacket the first time he fingered her. Or if the first girl a guy has sex with had her hair in a ponytail, he might need nothing more that to glimpse of a ponytail to become instantly erect.
Fetishes may include certain items of clothing. Bras, garter belts, stocking, panty-hose, lingerie, and high-heel shoes are considered erotic by many people. When someone has a fetish for this type of clothing, he or she many need to see it, touch it, or wear it to get aroused. Some people have fetishes for seeing their partner in a uniform from a particular job, such as a policeman, maid, cheerleader, or military officer. Some other common fetish outfits include clothes made of leather, latex, or rubber that are cut in a a style that displays the body in a sexually provocative fashion. This type of "fetish wear" is available (and expensive) from sex stores and catalogs.
Fetishes are a normal aspect of human sexuality. The fact is that some things are just more arousing to some people than they are to others. Fetishes are extremely individual. the only time that a fetish is problematic is if it gets in the way of someone's life or love life. For example, if a woman can't enjoy sex unless she's having it on an oak desk in a man's office, then her fetish for oak desks might become a problem. She might get caught having sex or work, or maybe she will cheat on her partner ever time she happens upon someone with an oak desk. However, most people can control their fetishes enough to enjoy sex and relationships, and hopefully, they are able to share their little eccentricities with their partners in a fun and healthy manner.
Source - The Complete Idiot's Guide to Amazing Sex