
Here's the meat of it - you shouldn't have any trouble following this:
In every couple, every pair of people, whether it's a wife and her husband, or two boys who are best friends, or a professor and his graduate student, or a bus driver and a passenger having an encounter - in ANY pair, there is always exactly one Boris, and exactly one Sergei.
Sergei is the smart one - or thinks he is, at any rate.
And Boris is the social one, who maybe isn't exactly bright, but he's certainly enthusiastic.
Sergei comes up with the plans, but Boris usually has to execute them - take the risks, essentially. Boris is happy with the arrangement, because he knows that he isn't smart enough to come up with the clever plans (Sergei constantly reinforces this notion Boris has about himself by frequently, and usually after filling Boris in on his responsibility, explaining Boris's hopeless naïveté to him).
Something one might often hear Sergei saying: "Boris, will you please be quiet! I'm trying to think!"
And Boris's response is usually something like, "But Sergei! I'm meeting people - this girls - to make connections!"
A fun game my son and I like to play - and I'm sure you will enjoy it, too - is "Which One is Boris?"
You can do this at the airport, at a restaurant, at the cinema before the movie starts…
Usually, once a pair is spotted, they'll betray their Boris/Sergei identity in short order.