Can someone explain what the two markers mean and the green margin?

Edit: i googled it 🤦‍♂️

The Eco gauge indicates how fuel-efficient the driving is:

With fuel-efficient driving, the gauge shows a low value with the pointer in the green zone.
With non-fuel-efficient driving, e.g. during heavy braking or heavy acceleration, the gauge shows a high value.
The Eco gauge also has an indicator to show how a reference driver would drive the car under the same driving conditions. This is indicated with a "diamond" on the gauge.