Here's why:
* Proverb: It's a short, well-known saying that expresses a common truth or belief. In this case, it conveys the idea that people often believe other people's situations are better than their own, but this is usually an illusion.
* Metaphor: It uses the image of grass to represent happiness, satisfaction, or a desirable situation. It implies that the grass, or life, is not actually better elsewhere, but people simply perceive it as such.
Let me know if you'd like to explore other examples of figurative language!