First off, welcome to the forum!
@ABC Gifts and Awards is a site vendor here, and offers great custom and semi-custom ceramic chips, and fantastic service.
Someone else may give more eloquent answers, but I'll take a crack at it:
Clay chips are made by compressing colored "clay" material in a mold, with a printed inlay impressed into the chip, or a hotstamp. Edgespots, colors, and design options are limited, but they have a great feel and sound, and wear in nicely. Cost is typically from $1.25/chip up to $4+. Only
www.classicpokerchips.com (also a respected site vendor,
@David Spragg) offers custom clay chips to the consumer market.
Ceramic chips start with a ceramic blank, and images are printed onto the blank. Design options are pretty much unlimited. Cost is typically less than $1/chip for ceramics. Quality ceramics look, feel, and stack great, and are practically indestructible.
First rule of PCF: Get samples!