A password is series of characters without any space. The main of password is to ascertain that a computer user seeking ingress to a computer system is truly the genuine user.
As a rule of thumb, the users of securely shielded single or multi user system maintain a unique name known as a user ID. To confirm that someone gaining access to that user ID truly is that person, a secondary identification, the password, familiar only to that person and to the system itself, is put by the user.
Password must contain one capital case letter, on lower case letter, one number and one special character ex: !,@, #, $ etc so as to have a very strong password.. With a aim to preserve the secrecy, password must be changed regularly.