What is SHA2? How does it work to ensure that an ISO image file you download is correct?

What will be an ideal response?

SHA2 (Secure Hash Algorithm 2) is a one-way hash function. A one-way
function takes a variable-length message and produces a fixed-length hash
(string of characters). When you run SHA2 against a file, it always produces
the same hash. If the file is changed, SHA2 produces a different hash.
When Fedora/RHEL creates an ISO image file, it runs SHA2 against the file
and publishes the resulting hash. After you download the file and run SHA2
against the downloaded copy of the file, if the resulting hash is the same as
the one Fedora/RHEL published, the file is correct.