Mode fuel consumption represents driving in a pattern (mode), combining stopping, acceleration, steady driving, deceleration and more.
There are various test methods depending on the country, including 10-15 mode and JC08 mode.
For example, company A may list fuel economy in urban areas in a catalogue. If company B lists suburban driving and company C lists highway driving, it won't be possible to compare them and see which company has the best fuel economy.
Therefore, fuel economy test methods (mode fuel consumption) are used by determining constant conditions for measuring fuel economy, so that we are able to compare fuel economy accurately.