So going this way, it's a binding curve, going backwards, it's a dissociation curve. And so we can use O two binding curve or O two dissociation curve interchangeably. These two terms mean the same exact thing. Now, on the graph, the y axis describes the fractional saturation of the protein. It tells us what fraction of the total number of proteins in our mixture is fully saturated, is bound to that oxygen, and it ranges from a value of zero to a value of one, where zero basically means none of the proteins contain oxygen, while one means 100% of the proteins or the proteins are bound to oxygen. Now, the x axis describes the concentration of the oxygen.