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The value produced by a hash function is the hash value or message digest. Hash functions are computationally feasible functions whose inverses are computationally infeasible. In practice, a password can be encoded to a hash value, but decoding remains infeasible. The equality of passwords can be tested through the equality of their has hash values.
A good practice is to always append a salt to the password being hashed. A salt is a unique (often sequential) or randomly generated piece of data that is stored along with the hash value. The use of a salt helps prevent brute-force attacks against the hash value, provided that the salt is long enough to generate sufficient entropy (shorter salt values cannot significantly slow down a brute-force attack). Each password should have its own salt associated with it. If a single salt were used for more than one password, two users would be able to see whether their passwords are the same.
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