base 4 is a positional numeral system with four as its base. It uses 4 different digits for representing numbers. The digits for base 4 could be 0, 1, 2, and 3.

base 8 is a positional numeral system with eight as its base. It uses 8 different digits for representing numbers. The digits for base 8 could be 0, 1, 2, 3, 4, 5, 6, and 7.