MD5 is an old cryptographic hash function that once helped verify data integrity, but it is no longer suitable for password storage. It is considered obsolete because it is very fast and has known weaknesses, which makes it easy to test against large numbers of password guesses.
In cyber security, MD5 matters when attackers obtain a password database. If passwords were hashed with MD5, they can often be cracked offline with brute force or precomputed tables, especially if the hashes were unsalted. That turns a data breach into an account takeover risk. Defenders avoid MD5 for passwords and use modern password hashing schemes such as bcrypt, scrypt, or Argon2, ideally with unique salts and strong rate-limiting on login attempts.