In which direction does the energy of a longitudinal wave move?

In a longitudinal wave, the energy travels parallel to the direction of vibration. This movement occurs because the particles of the medium through which the wave is traveling oscillate back and forth along the same axis as the wave itself. When these particles compress and then rarefy, they effectively transmit the wave's energy from one point to another in the same direction as their own movement, which is why the answer identifies the energy's direction as back and forth parallel to the direction of vibration. This characteristic differentiates longitudinal waves from transverse waves, where the energy moves perpendicular to the particle motion.