MD5 is often used in forums and software releases. It is a verification system designed to ensure the correctness of files and prevent some people from stealing programs, adding some Trojans or tampering with copyright.
Each file can use MD5 validator to calculate a fixed MD5 code. Software authors often calculate the MD5 code of his program in advance and publish it on the Internet.
So when you see the MD5 code next to a program download on the Internet, you can write it down. After downloading this program, use the MD5 verification program to calculate the MD5 code of the file you downloaded, and compare it with the MD5 code you wrote down before.
If they are the same, then what you downloaded is the original. If the calculated value does not match what is displayed on the Internet, then the file you downloaded is incomplete, or someone else has tampered with it.