Non-photosynthetic use of electron transport chains to generate ATP.
Cellular respiration, in eukaryotes, takes place in organelles known as mitochondria. In prokaryotes, the cell, in a sense is the mitochondria! (See, that is, endosymbiotic theory.)
Cellular respiration can involve a number of steps including oxidation of pyruvate (as formed via glycolysis), what is known as the Krebs citric acid cycle, and the donation of NADH to the electron transport chain, with NAD+ restored in the process.
A second coenzyme, known as FADH2 and also produced by the Krebs cycle, is able to donate electrons to the electron transport chain, in the process restoring its form which is known as FAD.
In the video note that reference to "anaerobic respiration" is incorrect and further that NAD+ and FAD are "coenzymes" rather than "enzymes":
Though is not directly involved in cellular respiration, in fact oxygen is used in the process and carbon dioxide is given off, thus providing the reason for why we breath. Contrast, though, with anaerobic respiration as well as fermentation.