Using the same password for multiple email, shopping and social networking websites is risky, it means that a security breach at one website will compromise all your accounts, possibly even leading to identity theft.
So, the idea is that you memorise just one, reasonably long, secure master password and use that to generate a set of non-dictionary passwords. Copy and paste the new password(s) into the website and set your web browser to remember them.
All the websites get different passwords, but you only have to remember one!
Using a different PC? you can re-generate the same set of passwords at any time by returning to this page and entering the same master password.
Password security - a comparison of Password Generators
Simon Sheppard, Feb 2018