SHA-256 (Secure Hash Algorithm 256) is a widely used cryptographic hash function. It is a one-way function that takes an input (message or data) of any length and produces a fixed-size output of 256 bits, which is known as a hash value or digest.

The main purpose of SHA-256 is to ensure data integrity and security by verifying that the data has not been tampered with or modified. This is achieved by comparing the hash values of the original and the received data. If the hash values match, it is highly likely that the data has not been altered during transmission or storage.

SHA-256 is used in a variety of applications, including digital signatures, password authentication, and blockchain technology. It is considered to be a highly secure cryptographic hash function and is widely trusted by the security community.