The events of Escape from Tarkov take place in an alternate universe around our present time, in the fictional Russian city of Tarkov, the northern industrial and financial center of the country, and its suburbs. The game events, in turn, set background for the Russia 2028 universe. The city of Tarkov is caught in a plight of the war between two private military companies, triggered by illegal activities of the Terra Group transnational corporation. For the reasons yet unknown, the situation in the city quickly went out of control and the local populace was evacuated. The only ones left behind were either private military contractors, the local Scavs gunmen or shady characters of unknown origin and allegiance.
The details of the story you can read at synopsis of EFT story.