Though .com domains are the most commonly purchased and used domains in the internet world, the use of country code domains is becoming increasingly popular. The IANA has an extensive list of country code domain extensions, most of which many of us have never heard of, and some we are starting to see more of.
The reason we are starting to see more of these ccTLD's popping up, especially .ca (Canada), .cn (China) and .uk (United Kingdom) is that many of them are registered with a direct and specific purpose in mind and therefore does a better job at targeting their desired audience. Unlike .com domains, these country code domains do less work making money being parked and are not generally purchased for this particular purpose.
May popular websites, such as Amazon and eBay, are using ccTLD's to target international customers outside of the US with specific versions of their website for those international shoppers.