In other words, if you buy your Nintendo 3DS in North America, only 3DS games bought in North America will function properly on your system.
There are three versions of the 3DS hardware, according to Nintendo: Japanese, American, and European/Australian. The Japanese and European versions of the Nintendo 3DS are likewise region locked.
The 3DS's older brothers, the Nintendo DS and Nintendo DS Lite, are region free. This means a person who owns a North American DS or DS Lite can purchase and play a Japanese or European game without being locked out or experiencing major technical problems. This excludes the Nintendo DSi and Nintendo DSi XL, which are region locked.
Nintendo explained its reasons for region locking the 3DS in a statement it sent to video game website VG247 in January 2011:
"Nintendo has developed different versions of Nintendo 3DS hardware to take into account different languages, age rating requirements and parental control functionality as well as to ensure compliance with local laws in each region. Nintendo 3DS also offers network services specifically tailored for each region.
"Additionally we want to ensure the best possible gaming experience for our users and there is the possibility that Nintendo 3DS software sold in one region will not function properly when running on Nintendo 3DS hardware sold in another. Guidance will appear on every packaging of Nintendo 3DS hardware and the accompanying software. If you are in doubt, Nintendo recommends that you only purchase Nintendo 3DS software in the region where purchased your Nintendo 3DS system."