As I remember, there were questions in russian in this site (russian se). now, when typing this quesion, I see a proof it was so, (I saw in suggestions of already asked questions): Whether to ask question in Russian or English (2 of 2 answers say that this site is bilingual). now I see there are 2 separate se sites for russian language, in russian and in english: Why is there a Russian Language and a separate Русский Язык SE Websites? . was that questions (that were in russian in this site) moved to the rus.stackexchange.com?
Historically, this site was a part of the original StackExchange network while our Russian sister site had been acquired later as a part of acquisition and merger of a Russian StackExchange network clone.
On this site, we try to be more friendly towards non-native Russian speakers and people with no knowledge of Russian whatsoever.
This site's interface is in English, it includes and encourages higher level of communication in English, and in our answers we try to not take the knowledge of Russian for granted when answering the questions. The ultimate goal is make the questions and the answers useful and comprehensible to those learning Russian or even curious of some aspects of Russian language without being able to actually speak it.
The questions explicitly asking for communication in Russian get moved to the Russian sister site (although this had happened but two or three times that I can remember).