Waves transfer energy without a net transfer of the medium. In transverse waves, oscillations are perpendicular to the direction of energy transfer; in longitudinal waves they are parallel. A floating marker oscillates as water-wave energy passes, while sound involves air-particle oscillations producing compressions and rarefactions. Example: Explain a floating cork remaining near its original position as ripples pass. It oscillates locally while energy travels onwards. Avoid unjustified claims.