Answer Description
By force expiring all passwords, every network user will be required to change their password at next login. This is a good method to reset all passwords if you suspect some have been obtained maliciously.
Wikipedia
A password, sometimes called a passcode, is a memorized secret, typically a string of characters, used to confirm the identity of a user Using the terminology of the NIST Digital Identity Guidelines, the secret is memorized by a party called the claimant while the party verifying the identity of the claimant is called the verifier When the claimant successfully demonstrates knowledge of the password to the verifier through an established authentication protocol, the verifier is able to infer the claimant's identity In general, a password is an arbitrary string of characters including letters, digits, or other symbols If the permissible characters are constrained to be numeric, the corresponding secret is sometimes called a personal identification number (PIN)
Password - Wikipedia, the free encyclopedia