Gamma Exposure
Gamma exposure describes how strongly Delta is expected to change as the underlying price moves. At the market level, Gamma exposure metrics attempt to estimate the aggregate Gamma associated with outstanding options positions, often using assumptions about who holds which side of those positions.
Why it matters to you
GEX is frequently used to estimate how options positioning might influence hedging flows. However: GEX is a model, not a direct view into every dealer's book. Different data providers may calculate it differently.