Trust me it's a thing.
Filofax is a company that sells organizers. They are normally leather and you could say a 6 ring binder.
Someone can do a whole A-Z on them.
There are many usages. I have a 5 year journal, 30 lists, dream journal, gratitude journal, art journal, knitting journal, finance binder and I have found out that I am an A5 girl. Also have a nice stash of washi tape and stamps to make it all pretty.