Update README.

Author: trekhleb

README.md

@@ -62,7 +62,7 @@ the data.
   * `A` [Segment Tree](src/data-structures/tree/segment-tree) - with min/max/sum range queries examples
   * `A` [Fenwick Tree](src/data-structures/tree/fenwick-tree) (Binary Indexed Tree)
 * `A` [Graph](src/data-structures/graph) (both directed and undirected)
-* `A` [Disjoint Set](src/data-structures/disjoint-set)
+* `A` [Disjoint Set](src/data-structures/disjoint-set) - a union–find data structure or merge–find set
 * `A` [Bloom Filter](src/data-structures/bloom-filter)
 * `A` [LRU Cache](src/data-structures/lru-cache/) - Least Recently Used (LRU) cache