I don't know what you mean by buying a train in gondola, but I can tell you what gondola is. The gondola car is one of the vehicles that transport goods by railway. This kind of car has no roof and is mainly used to transport bulk goods, such as yellow sand, iron ore and coal. Carriage is just a common name. For example, one owner asks another owner, "How many wagons did you install today?" Answer: "three cars" or "three wagons."