What is a one-time password? Can't access my Square Enix account

I signed up to a SE account some time ago, it was the only time I logged in their account system. When I tried accessing it again yesterday to pre-order a game from their store it asked me to login with my SE account, which requires 2 passwords? I'm sure I signed up with 1 password, I even

Getting Started, Game Manual

SQUARE ENIX Support Center - SQUARE ENIX Account

SQUARE ENIX The Official SQUARE ENIX Website

SQUARE ENIX Support Center - SQUARE ENIX Account

XIVLauncher Authenticator App

How to access FFXIV Online: one-time password, free trial version - Dexerto

SquareEnix Security Token available

SQUARE ENIX Support Center - SQUARE ENIX Account

Using a Square Enix Account, FFXIclopedia

SQUARE ENIX The Official SQUARE ENIX Website