Hashing is a technique used in data structures to map keys and values into a hash table using a hash function. It is done for faster access to elements. The hash function generates a fixed-size output from an input of variable size, which determines an index or location. Hashing is used to quickly identify a specific value within a given array. The hash table then uses the hash function to generate an index, and hashing uses this unique index to perform insert, update, and search operations.

The efficiency of mapping depends on the efficiency of the hash function used. The hash function takes an input (such as a string or number) and returns a fixed-size value, which is used as an index in the hash table. The hash function should be designed to minimize collisions, which occur when two different keys are mapped to the same index.

Hashing is used in various real-life applications, such as indexing in databases, disk-based data structures, and implementing objects in programming languages like Python and JavaScript. Hashing is also used in digital signatures to encrypt and decrypt messages.

In summary, hashing is a technique used in data structures to map keys and values into a hash table using a hash function. The hash function generates a fixed-size output from an input of variable size, which determines an index or location. Hashing is used to quickly identify a specific value within a given array, and the efficiency of mapping depends on the efficiency of the hash function used.