It doesn't aply for every tagged game but in essential it does mean that the game is bought in Russia or an East-European country in the CIS region. Some games are unplayable if you're outside of this area, Some do work however (such as fallout new vegas). if you're not from this region I advice you to stay away from these copies. every game that is region locked will show up with a orange box on the steamstore page in the given country.
well, I have no clue, to be absolutely sure just don't trade for these locked games. I've only encountered Fallout new vegas to be legit and playble with English language. Most games won't even activate to your account tho.
If the other trader said it will work, and if they have a high rep (meaning over 100 with little to no negative), then I would say it's okay. Just ask if you can return it for a refund if it doesn't activate for you.
i wanna buy splinter cell but i see :
Tom Clancy's Splinter Cell Blacklist Deluxe Edition RU+CIS
And i m afraid it doesn't work