A salt is a unique, random value stored alongside a password hash and combined with the password during hashing. Its main security benefit is that it ensures identical passwords do not produce identical hashes across different accounts or systems. If two users choose the same password, their stored hashes will differ because their salts differ, which directly prevents attackers from spotting shared passwords by comparing hashes. Salts also defeat precomputation attacks such as rainbow tables, because an attacker would need to regenerate tables for each possible salt value---a task that becomes infeasible when salts are large and unique per password. Salt does not enforce password complexity rules (that's a policy/validation function), does not guarantee users choose different passwords, and does not prevent password reuse across sites. The correct statement is that salt makes the resulting hash different even for the same password, improving resistance to offline cracking at scale and eliminating the ''same hash = same password'' shortcut attackers rely on.