Linked from
The 40 pages that link to Characteristic function, each with the reason it gives.
Power setRelated: Each subset corresponds to a binary inclusion pattern on the original set.
Cantor's theoremRelated: It represents each subset as a function, enabling the diagonal proof.
MultisetRelated: Multisets use the analogous count function, whose values can exceed one.
Random vectorRelated: Its multivariate version uniquely determines a random vector's distribution.
CodeRelated: It converts a set into a numerical representation.