Question: This term seems to be quite in use in English-speaking communities. I'm curious what it is? Is it like two students code together on a single PC or what? Is this organization (whatever it is) is only used in US?

Answer: 
When in doubt, ask Wikipedia: [Pair Programming](http://en.wikipedia.org/wiki/Pair_programming). The general idea is to have one person writing code while the other scans for mistakes and cohesiveness.
An extension of Pair Programming sometimes used by practitioners of [Test Driven Development](http://en.wikipedia.org/wiki/Test-driven_development) is [Ping Pong Pairing](http://c2.com/cgi/wiki?PairProgrammingPingPongPattern).

Ping Pong Pairing works something like:  

* Write a failing test (developer A)
* Implement code that makes the test pass then (optionally) [Refactor](http://en.wikipedia.org/wiki/Refactoring) (developer B)
* Write a failing test (developer B)
* Implement code that makes the test pass then (optionally) Refactor (developer A)
* and so on...

One of the benefits of Ping Pong Pairing is that it's tough for either developer to sleep very long ;-)