Quoted from
wikipedia:Apperception
In philosophy, Immanuel Kant distinguished transcendental apperception from empirical apperception.
The first is "the pure, original, unchangeable consciousness that is the necessary condition of experience and the ultimate foundation of the unity of experience."
The second is "the consciousness of the concrete actual self with its changing states," the so-called "inner sense." (Otto F. Kraushaar in Runes[1]).
[1] Runes, Dagobert D. (ed.), Dictionary of Philosophy, Littlefield, Adams, and Company, Totowa, NJ, 1972.