Linked from
The 9 pages that link to Remainder, each with the reason it gives.
Modular arithmeticRelated: Equality of remainders is the intuitive test for congruence.
DivisibilityRelated: A zero remainder is equivalent to exact divisibility.
Long divisionRelated: The remainder from one step is combined with the next digit.
ArithmeticRelated: Remainders complete whole-number division when the quotient is not an integer.
Even numberRelated: The remainder modulo 2 distinguishes even integers from odd integers.
BaseRelated: Each remainder in repeated base division supplies one digit.