The market's mood ring. A single number that tells you how the crowd feels about Bitcoin — and why doing the opposite usually works.
Imagine a trendy new nightclub called "The Moon."
Extreme Greed (80-100)
The club is over capacity. People are bribing the bouncer to get in, the dance floor is so packed you can't move, and everyone inside is convinced the party will never end. This is when the balcony is most likely to collapse — there's too much weight (capital) and nowhere left for new people to stand.
Market reality: When everyone has already bought in, there are no "new buyers" left to push the price higher.
Extreme Fear (0-20)
A small fire starts in the kitchen (a bad news headline). Someone yells "Fire!" and everyone rushes for the one tiny exit at the same time. People are tripping over each other, dropping their phones, and sprinting away from the building. Ten minutes later, the building is still standing, the fire is out, and the club is totally empty.
Market reality: The assets are still there, but because everyone ran away in a panic, you can walk in and pick up the "phones" (Bitcoin) they dropped for a fraction of the price.