These mean that the character is outwardly "Speaking".
Ex: Arata looked down, words laced with a hint of disappointment "If you won't do it, then I will do it for you".
These mean that the character is inwardly 'Thinking'.
Ex: 'Perhaps they are not as crazy as they seemed at first' Arata thought, but quickly dismissed the notion.
Brackets are used for [Informational Exposition or Instructions]
Ex: [2 Years Later] or [Arata's Perspective]
Parentheses is used for (additional information throughout the writing)
Ex: L.W.E.A.M.C. (Like When Explaining Abbreviations or Making Callbacks) or (When explaining things that cannot be explained through a character and I am too lazy to switch to a 3rd Person Exposition just for a little explanation.)
[Relevant]
(YES, the Guidelines were made after the Short Prologue, that's why it's different, don't mind it though)