Since hash functions are also deterministic (meaning that the same input produces the same output), comparing two password hashes (the stored one and the hash of the password provided by a user) is almost as good as comparing the real passwords. Hash functions are designed to be one-way, meaning that it is very difficult to determine the input that produces a given output. Instead, authentication systems store a password hash, which is the result of sending the password - and a random value called a salt - through a hash function.
This would make it far too easy for a hacker or a malicious insider to gain access to all of the user accounts on the system. A well-designed password-based authentication system doesn’t store a user’s actual password.
