What does CIS mean i hear a lot of people using the word but isnt it like a military group or terrorist group?
It's short for Commonwealth of Independent States it contains countries like Russia and it's neighbours. Here's a wikipedia link for more info https://en.wikipedia.org/wiki/Commonwealth_of_Independent_States
Former Soviet Union states excluding Baltic countries(Moldova is also mostly excluded), it was a special zone as it's trans-continent(including Caucasus and Central Asia) and Russia dominating.
Valve formerly seemed CIS as a major region but after Russo-Ukraine War the region was renamed Eastern Europe while Riot suspended its competitions in CIS.