Foot fetishes are actually very common, and are amongst the most frequently mentioned fetishes in popular media. The feet are a body part sometimes associated with smell and unattractiveness, which gets some people's taboo centres working. They're also erogenous zones for many, particularly as most people aren't that used to having them touched. Boots, heels and other footwear are precisely the kind of sexualised accessories so many people fall for, meaning that the feet inside them can also end up as the object of someone's desire. There are tonnes of feet videos and feet pictures online for those who can't get enough of pretty feet.
If you have a foot fetish, you might find that you're especially drawn to a certain kind of foot: large feet, small feet, ones in see-through shoes or bare feet.