Hashing is used to store passwords and transfer important data securely via encryption. Secure Hash Algorithm 256 (SHA-256) is a cryptographic algorithm that is used for hashing. In simple terms, it generates a unique fingerprint for each set of data on your website (such as your website certificate). Then, only those with that unique digital fingerprint can decrypt or modify that information, keeping it secure.
SHA-256 was developed by the National Security Agency (NSA) at the turn of the century and is the gold standard for website encryption. To check whether your website is using it, you can inspect your website certificate in your browser or use an online certificate inspection tool.
If you find that your certificate shows your website is using SHA-1, you should strongly consider getting this reissued with SHA-256.