The seats in business class are different from those in first class. Business class is generally a row of two people, between first class and economy class, while first class is generally located in the front of the cabin. Business class and first class enjoy different services, and their prices, waiting methods and boarding methods are different. The simple explanation is:

The first class car is soft sleeper.

Business class = business class. It's a hard berth.

Economy class is a hard seat for green leather cars.

There is also a so-called value-added economy class, which can be understood as a dining car.