Unique user names and secure passwords are used by systems to distinguish between authorized users and unauthorized individuals. While username generation is often standardized, thus easy to deduce about another individual, passwords are an authentication factor that only you should know and should be complex enough that they cannot be easily guessed or compromised through brute-force (i.e.: try every possible combination) methods. When your credentials are compromised, not only can an unauthorized individual access your system or data, but they are doing so "as you". This is also an issue if you choose to share your password with a colleague, as ultimately you will be responsible for any actions they perform or comprises that occur during their usage. By taking the time choose a secure password and adhering to best practices regarding it's safety and protection, you can limit the chance of such a compromise.