Explain what a "hash table" is.

A hash table is a data structure that implements an associative array using a hash function. This means it allows data to be stored in key-value pairs, where each key is processed through a hash function to determine a specific index in an array where the corresponding value is stored.

The use of a hash function is crucial because it generates a unique index for each key, facilitating quick data retrieval. When a key-value pair is added, the hash function computes the index, and the value is stored at that index in the array. To retrieve a value, the same hash function is applied to the key, yielding the index where the value resides, thereby allowing near-constant time complexity for lookups, insertions, and deletions under optimal conditions.

This structure is optimal for scenarios that require frequent access and modification of data, making hash tables particularly useful in implementing dictionaries or sets. Additionally, while hash tables can experience collisions (where two keys hash to the same index), methods such as chaining or open addressing help manage these and maintain efficient performance.

In contrast, the other options describe different concepts. A. refers to linear data structures like arrays or linked lists; C. discusses data sorting, which is unrelated to the associative retrieval feature of hash tables;