Gamma vs Vega

The rate of change of delta relative to a $1 change in the underlying price; highest for at-the-money options near expiry; long options have positive gamma; short options have negative gamma; high gamma positions are unstable and require careful management near expiry.

The rate of change of an option's price relative to a 1% change in implied volatility; long options have positive vega (gain value when IV rises); short options have negative vega (lose value when IV rises); the primary risk in bought options around anticipated events.