A transit country is a country a shipment passes through between its origin and destination without the goods being cleared for domestic use there; the vehicle moves under customs control, covered by a transit document such as a TIR Carnet or a T1, and does not clear full import duties on that leg.
Which countries a shipment transits, and which transit document covers each one, depends on the specific route and the countries' customs regimes. See Turkey to Central Asia Road Routes for how this plays out on Dealti's own corridors, and TIR Carnet or T1 for the documents themselves.
