The strategy described involves taking three different option positions on the same underlying asset with the same expiration date but different strike prices:

1. Long one call option at a lower strike price ($X_1$)
2. Short two call options at a middle strike price ($X_2$)
3. Long one call option at a higher strike price ($X_3$)

(Note: While the bracketed text $(X_1 > X_2 > X_3)$ contradicts the descriptive text in the question which states $X_1$ is the lower strike and $X_3$ is the much higher strike, the structural setup of buying one option, selling two at a middle strike, and buying a third option defines the strategy.)

A strategy involving long 1, short 2, and long 1 on three consecutive equidistant strike prices is classically defined as a Butterfly spread. It is designed to profit when the underlying asset's price remains stable and close to the middle strike price ($X_2$).