A hash function is a mathematical function that is used to map data of any size to a fixed size output. The purpose of a hash function is to provide a way to store data in a secure and organized manner.
For example, a hash function could be used to create a digital fingerprint for a file. The fingerprint is created by running the contents of the file through the hash function, which produces a unique output. This output can then be used to compare the contents of the file to make sure it has not been modified.