Everything is energy. Every solid matter as dense as rocks, stones and minerals are energies, and every nonphysical experience, such as thoughts and emotions, are as well energies.
The easiest way to understand or comprehend and perceive energies are those using our senses, such as seeing, touching, tasting, smelling and hearing. And one that takes the most direct form (omitting the necessity of any interpretation/translation from our mind) is sound. We could hear as well as feel the vibrations of sound.
An intention to heal and uplift paired with a medium/a frequency/a vibration - such as sound from the Crystal Singing Bowls, to transmit that energy becomes a powerful healing modality.