Bullet Journals

[fellinara]

Hi Everyone! I'm pretty new to bullet journalling and am looking at getting a Leuchttrum 1917 journal. Amazon has them on Prime for just shy of $20. I'm currently using a small temp bullet journal for August to get an idea on what spreads and collections will work for me and which ones are not really. I see that these journals/notebooks (also Moleskine and a few other brands)use a system of type of journal(??) such as A5, A6, etc. New to the bullet journal movement, I am not entirely sure what that means. I figured if anyone knows, it will be here.

Thanks!