SHA-256 is a member of SHA-2 (Secure Hash Algorithm 2) cryptographic hash functions family designed by United States NSA. The resulting hash value of SHA-256 is 256 bits (32-bytes) long. This provides a larger search space compared to SHA-1 and makes it infeasible to reverse engineer to retrieve the original input.
SHA-256 is used to ensure security in many use cases such as digital signatures, password hashing, blockchain technology, file integrity, SSL/TLS certificates, etc.