The purpose of password is to protect data stored on a computer. It protects data from being lost, misused or deleted by any person. The system can be accessed by a person who knows the password. Password can be changed only by authorized person. An unauthorized person cannot access a computer system or program that is protected by a password. So the computer and the data stored on it will be safe and protected.
Every computer provides an option for setting password. If the computer is protected with password, it will ask for that password to login.
Email facility on the internet is also protected with password. Every user has to give email ID and password to check emails.
Internet service providers provide user account with passwords. The user ID and password is used to connect to the internet.