whats the difference??

HI I'M interested too because I have listed a keychain but wonder if it should be a Keyfob

well i looked at both categories and the contain similar items - so i think there may be lots more people pondering this!

well according to dictionary.com:

A key fob is a generally decorative and at times useful item many people often carry with their keys, on a ring or a chain, for ease of tactile identification, to provide a better grip, or to make a personal statement. Key fobs are often called "key rings" or "key chains" in colloquial usage. The word fob may be linked to the low German dialect for the word Fuppe, meaning "pocket", however, the real origin of the word is unknown.
Fobs vary considerably in size, style and functionality. Most commonly they are simple discs of smooth metal or plastic, typically with a message or symbol such as that of a logo (as with conference tchotchke) or a sign of an important group affiliation. A fob may be symbolic or strictly aesthetic, but it can also be a small tool. Many fobs are small flashlights, compasses, calculators, penknives, discount cards, bottle openers, or USB flash drives.
and A keychain or key chain is a small chain, usually made from metal or plastic, that connects a small item to a keyring. The length of a keychain allows an item to be used more easily than if connected directly to a keyring. Some keychains allow one or both ends the ability to rotate, keeping the keychain from becoming twisted, while the item is being used. A keychain can also be a connecting link between a keyring and the belt of an individual. It is usually employed by personnel whose job demands frequent use of keys, such as a security guard, prison officer, janitor, or retail store manager. The chain is often retractable, and therefore may be a nylon rope, instead of an actual metal chain. The chain ensures that the keys remain attached to the individual using them, makes accidental loss less likely, and saves on wear and tear on the pockets of the user.

so according to this there are items in the keychain bit that should be in keyfob - including mine!

I just had the same problem, while trying to list some new stuff. According to Wikipedia, a fob is the actual item that hangs from the chain, whereas the chain is... just that: the chain. I took it as such and listed my key-thingies as fobs. :>