What is the meaning of the green arrow in the traffic light?

1. Keep driving straight or right only.
2. Correct answer: You may continue driving in the direction of the arrow only.
3. Only public vehicles are permitted to turn in the direction of the arrow.
4. Cross the intersection and clear it quickly, in every direction you want to go.

WhyA green arrow lets you go only in its direction. It does not open other directions.