OVERWRITE FOLDER: The overwrite folder is found at the bottom of the left pane, and is used to store files MO doesn't recognise, because it doesn't know where to place them. These files are typically newly created files, usually generated by an external mod tool (i.e. Wrye Bash, xEdit, FNIS, ...).

Where is the overwrite folder?

The "overwrite" folder contains files that "replace" other files in the "install order". In this instance it is showing your that there are files under the "uio\public", "menus\options", and "menus\main" sub-folders which overwrite previously installed versions of those files. That is by design.

Where are mod organizer 2 mods stored?

Mod Organizer has two mods: Instance and Portable. If you are using Instance mode (the default), your downloads, profiles, and mods folder are stored in %LocalAppData% (usually C:\Users\[username]\AppData\Local\ModOrganizer).