What is a password?
Generally speaking, passwords are a string of characters – either numbers, letters, or special characters – that can be used to log on to a computer and access programs, resources, and files. Passwords are designed to ensure that unauthorized people are unable to access your computer. Most passwords can be made up of a combination of symbols, spaces, characters and numbers, and these passwords can also be case-sensitive.
To ensure that your computer information stays secure, you should never give your password to another person or write it down in an easily accessible location!
Read this Wikipedia password article for more information.