SHA-256 produces a 256-bit (32-byte) hash value.
What is SHA-256?
The SHA (Secure Hash Algorithm) is one of a number of cryptographic hash functions. A cryptographic hash is like a signature for a text or a data file. SHA-256 algorithm generates an almost-unique, fixed size 256-bit (32-byte) hash. Hash is a one way function – it cannot be decrypted back. This makes it suitable for password validation, challenge hash authentication, anti-tamper, digital signatures.
SHA-256 is one of the successor hash functions to SHA-1, and is one of the strongest hash functions available.
With this online tool you can easily generate hashes.
This is the actual function used for mining Bitcoin.