Load order explanation - what overwrites what?

[Bogdanov89]

I apologize for this very amateur question but i do not understand which mod will take priority (overwrite the others) - the mod that is at # 0 or the one that is at # 3 (considering i have 4 mods in total)?

I am trying to troubleshoot a mod not loading and i can not find a clear answer. (i am using the Full release mod fixer with message remover) Thank you for helping me out.