Hashing

A hash function takes bits of any length. It runs operations on them. The output always has a fixed length.

For SHA256, the output is always 256 bits. The final form is in hexadecimal. Every 4 bits become one hex character. The final output has 64 characters.

Word Size

Programming languages parse bits into sizes based on the data type. In the same way, a hash function works on raw bits. It splits the data into its own preferred size.

SHA 256 splits the data into 512 bit words. Then it works on these words to make the final hash.

Checksum

A checksum is also like hashing. But its use case is different. It doesn't secure data. It only checks data integrity.

hashing is for security, checksum is for integrity

Hashing is for cryptographic security. A checksum is for data integrity.