MD5 is a hashing algorithm. It was developed by Professor Ronald L. Rivest of the Massachusetts Institute of Technology in 1991. With it, you can create checksums or "fingerprints" of messages of arbitrary length and then verify their authenticity. MD5 has been remade from MD4.
Password hashing with the MD5 algorithm has also become widespread. When a user registers in any system, then the password is saved not in text form, but in the form of an MD5 fingerprint. When logging in to the system, the entered password is encrypted each time and checked against the fingerprint stored in the system.