I couldn't figure out what CSTO was: I found out it is something similar to NATO with Russia as it's center and surrounding countries it influences

 Here is a map of CSTO (Russian Version of NATO):

Begin partial quote from:

https://www.civilsdaily.com/news/pib-collective-security-treaty-organization-csto/

The Prime Minister has participated virtually in the Joint SCO (Shanghai Cooperation Organization)-CSTO Outreach Session on Afghanistan.