Yeah, exactly. Commonly, the salts are stored right next to the hashes in the DB, because they serve their purpose even if the attacker knows what the salts are

Yeah, exactly. Commonly, the salts are stored right next to the hashes in the DB, because they serve their purpose even if the attacker knows what the salts are. By using a different salt for every password, the attacker needs execute a full "guess, hash, compare, repeat" attack on each user, as opposed to "guess, hash, compare against all user passwords, repeat" on the entire database.