Fatty acid oxidation break down a fatty acid in units of 2 carbons. A good and crude visualization of this is the removal of 2 slices of bread from a loaf of bread. In this case the loaf has 16 slices, sort of a palmitc acid as loaf of bread association. As the loaf of bread is oxidized for energy, 2 slices of bread are removed from one end. These are then used to make a sandwich or put carbons into the citric acid cycle.