What separates the two is their method of delivery.

两者的区别在于它们的交付方式。

The company has experimented with several methods of delivery vehicles, helicopters, electric bikes, self-driving cars, even cars with a heated pizza oven.

该公司已经尝试了几种运输工具：直升机、电动自行车、自动驾驶汽车，甚至是带有加热披萨烤箱的汽车。