A hash map is a data structure that stores key-value pairs, allowing for efficient data retrieval. It uses a hash function to convert keys into unique indices, which helps in quickly locating the corresponding values. This makes hash maps particularly useful for tasks like searching, inserting, and deleting data. In a hash map, if two keys produce the same index, a collision occurs. To handle collisions, various techniques like chaining or open addressing are used. Hash maps are widely used in programming languages and applications, making them an essential concept in computer science and software development.