We had been anticipating a global launch of the Facebook Tag Suggestion feature for quite some time, given that it had been sporadically available to a handful of its users already. The feature simply helps ease the task of tagging friends in pictures. This is done simply matching the existing tagged photos in your albums or those of your friends to detect faces and suggest tags.
As mentioned the feature had already been rolled out in the US and some users globally, but the current announcement is more public regarding the Tag Suggestions. Facebook has officially not named what countries have been included recently. I guess the period of testing has been pretty fruitful and has worked in the favor of the social network that it is finally being rolled out.
The feature is turned on by default. Users will have to go to their privacy settings and turn it off using the Suggest Photos of me to friends to rid yourself of Facebook auto tagging your pictures.