base 10 is a positional numeral system with ten as its base. It uses 10 different digits for representing numbers. The digits for base 10 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9.

base 20 is a positional numeral system with twenty as its base. It uses 20 different digits for representing numbers. The digits for base 20 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f, g, h, i, and j.