The video shows train bogie changing at Erlian border station in China after crossing the border from Mongolia on the Trans-Mongolian Railway, running from Moscow to Beijing.
Russian and Mongolian gauge is 1520 mm, while China, Europe and North America use what is called "Standard gauge" with a width of 1435 mm. The first is installed on 220 000 km of railway lines while the last is laid down on some 720 000 km. Source: Wikipedia
