WordPress has tons of themes and they are all different. Depending on your customizations specific processes need to be documented. A quick change can turn into a major ordeal if this step is disregarded. This WordPress Theme Info sheet helps you remember exactly how specific elements integrated into the CMS.
Robust systems are great when it comes to keeping all your information in one place. But when you take advantage of all the widgets, plugins and add-ons there are lots of passwords you will need to keep track of.
Another reason that you may want to have this information at hand is if you need to hire someone to make changes to your site OR if you are changing the company who manages your site. I’ve come across a few places where you have to fight to get the login information.
A little about WordPress:
WordPress is a content management system based on PHP and MySQL that is usually used with the MySQL or MariaDB database servers but can also use the SQLite database engine. Features include a plugin architecture and a template system, referred to inside WordPress as Themes.