How does the electron transport chain work?

The electron transport chain is a collection of proteins (complexes), of which there are 4 types, whose purpose is to pump protons into the intermembrane space. These protons will be used by the ATP synthase in order to create ATP, which will be used as an energy currency.

The electron transport chain interacts with reduced NAD and reduced FAD, which give up their H⁺ to the proteins of the chain to be pumped out and their electrons to the same proteins to be passed from one complex to the other down an energy gradient. The energy is used to pump H⁺. When the electrons reach the last protein of the chain, they are released into the matrix where they, along with H⁺ coming from ATP synthase, reduce O2 to water.