A "Base Number" refers to the foundational number in a numeral system that determines how numbers are represented. For example, in the decimal system, which is base 10, the digits range from 0 to 9. In contrast, the binary system is base 2, using only the digits 0 and 1. Base numbers are crucial in mathematics and computer science, as they influence calculations and data representation. Different bases can simplify certain operations or make them more efficient, such as using base 16 (hexadecimal) in programming to represent large binary numbers more compactly.