Option quotes are different in price and in volume because identical options can trade on more than one market or exchange. Typically, the main options exchanges in the U.S. are the American, Pacific, Chicago and Philadelphia exchanges. If you were looking at a particular call option with a specific strike price and expiry, it's likely that the option will be trading on more than one exchange but at a different price on each one. Quote providers may be giving you dissimilar information because they are receiving their numbers from different sources. However, while discrepancies do occur between exchanges, the prices will gravitate to a common level if investors look for the lowest quote when buying an option.
(If you are new to the world of options and would like to learn more, check out our Options Basics Tutorial.)