A disjoint-set data structure, also known as a union-find data structure, is used to manage a collection of non-overlapping sets. It supports two primary operations: union, which merges two sets, and find, which identifies the set containing a particular element. This structure is particularly useful in scenarios like network connectivity and clustering. Disjoint-set data structures are often implemented with optimizations such as path compression and union by rank. These techniques enhance performance, making operations nearly constant time, which is efficient for large datasets. Applications include algorithms for minimum spanning trees and dynamic connectivity problems.