It does not involve the same level of coordination and cooperation seen across most of the European Union countries, but a certain level of economic and political collaboration between CIS states does exist.
Ukraine was de facto participating in the Commonwealth until 2018 but was never an official member. Ukraine announced its withdrawal due to the Russian occupation of Crimea. Georgia was also a part of the CIS until 2009.
Turkmenistan has participated since 1991 but has not become a full member.
Participating states have had generally friendly relations with Russia since the fall of the Soviet Union, and you will frequently find Russian speakers in these countries, even those born after 1991. In some regions you will find more Russian speakers than speakers of the native language, especially in Belarus and northern Kazakhstan. Non-participating states usually have fewer Russian speakers (except for Ukraine) and often have a less pro-Russian sentiment. Those who do still speak some Russian in these states may prefer not to use it.