On the question on how he could keep track of every person, culture, nation, etc., Robert Jordan answered that he had a file for every person, nation, city, culture, etc., describing it. In the case of persons, traumatic experiences, origin, favorite foods and colors, family, education, etc., is stored. Every person that appears several times, or has the chance to appear several times has a such file. Similar information is stored on the other entities. This information is used to flesh out the characters etc. and make them three-dimensional before the book itself is written.
Part of this information is going to be given in the Guide to the WoT books that is going to be published this autumn, but far from everything.
If you are viewing this on github.io, you can see that this site is open source. Please do not try to improve this page. It is auto-generated by a python script. If you have suggestions for improvements, please start a discussion on the github repo or the Discord.