My go to source is libretext. Glucose is transformed to pyruvate then Acetyl CoA. The Krebs or Citric Acid cycle creates electron carrier molecules. These donate electrons and power four proteins which slowly pump protons into the mitochondria space between its inner and outer membrane. This creates a proton gradient or imbalance as the protons want to diffuse back into the mitochondria. This flow or river of protons power the ATPsynthase which is like a wind turbine and creates ATP for the cell to use.
What is interesting is that plants create glucose in their leaves. But plant cells also consume glucose at night. Or in parts of the plant that cannot create its own energy.
So "oh it's a water wheel that the proton pushes that then pushes the phosphate onto the ADP" is like, "Oh. There's...a whole physical machine and not just magic 'energy transfer'". I just thought it was really cool, though obvious in retrospect.
(I am not a clever man.)