High-speed rail (G/D/C trains) has three classes. Here's what you get for each.
Second Class (二等座)
Price: Baseline
Seat: 3+2 configuration, airplane-style
Space: Adequate for trips under 4 hours
Best for: Budget travelers, short trips
First Class (一等座)
Price: ~1.6x second class
Seat: 2+2 configuration, wider, more legroom
Space: Comfortable for 4–8 hour trips
Best for: Medium-distance, business travelers
Business Class (商务座)
Price: ~3x second class
Seat: Lie-flat pod, premium food, dedicated lounge
Space: Luxurious, comparable to airline business class
Best for: Trips over 6 hours, splurge occasions
Pro tip: Book via Trip.com in English. For popular routes (Beijing–Shanghai), book 15 days ahead.