A password, along with a user name, is a security measure that allows you access to a computer system, application, email service or online service. A password varies in length and can contain alpha as well as numeric characters and symbols. Short, simple words, phrases and numbers result in weak passwords that hackers and other individuals can simply guess. Once you have a secure password created, it is important to memorize it, but you can write it down.
Password strength is a measure of the effectiveness of a password in resisting guessing and brute-force attacks. In its usual form, it estimates how many trials an attacker who does not have direct access to the password would need, on average, to guess it correctly.