What does it mean to change seats on the high-speed rail ticket?

The high-speed rail ticket shows that changing seats in the train means that passengers can change seats when there are vacant seats in the train. Under normal circumstances, the seats of high-speed trains are fixed. Passengers need to choose seats when purchasing tickets, and they need to find seats according to the ticket information when riding. However, in the car, if there are spare seats, the flight attendants may allow passengers to change seats to improve seat utilization and ride comfort. It should be noted that changing seats on the train requires the permission and guidance of the flight attendants, and it is not allowed to change seats at will, so as not to affect other passengers and train operation.