What is the primary feature of a hash table?

The primary feature of a hash table is that it employs a hash function to compute an index into an array of buckets or slots. This indexing allows for efficient data retrieval, insertion, and deletion operations. When a key-value pair is added to the hash table, the hash function processes the key and returns an integer, which represents the index where this value should be stored in the underlying array. As a result, hash tables can achieve average-case time complexity of O(1) for these operations, making them very performant for certain applications.

While other structures like binary trees are organized based on their values and allow for ordered data retrieval, hash tables focus on direct access through computed indices. The structure of a hash table does not maintain a sorted order, and while hash tables can technically store unique keys, this is not the defining characteristic of a hash table compared to its use of a hash function.