$ETH refers to "aerobic respiration," such as the breathing you do when jogging slowly or walking.

● How it works: Your body "burns" the food you eat (like sugar) together with the oxygen you breathe in to produce energy (so you have strength) + carbon dioxide (the air you exhale) + water (sweat or urine).
● Advantage: Lots of energy! Like a "high-power power plant," 1 unit of sugar can generate 38 units of energy (ATP).
● Who uses it: Humans, animals, and plants (during the day) use it most of the time.
Example from daily life:
You can walk for half an hour without getting tired because aerobic respiration slowly provides energy, like a long-lasting power bank.