We require passwords to be 8+ characters and to be reasonably difficult for someone to hack.
This means:
The password isn't one of the 10,000 most common passwords (e.g. "password", "12345678" or "sunshine")
The password isn't one of the 10,000 most common passwords simply replacing letters with numbers or adding an exclamation mark (e.g. "p4ssw0rd!" or "5un5h1n3")
The above passwords can be discovered using hacking tools in less than a second (!)
We recommend that you either:
Generate a password using a password manager (e.g. LastPass)
Or use a combination of 3 or 4 words. Like "Cow Eat Lemon" or "Oh A Dog Hat". These passwords are very secure against hacking, and very easy to remember.