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 25 is a positional numeral system with twenty-five as its base. It uses 25 different digits for representing numbers. The digits for base 25 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f, g, h, i, j, k, l, m, n, and o.