Folder structure overview - storage and cache.

I am totally confused on the OC folder structure "should-be" and also why. Please bare with me being an OC noob.
At the moment i have - in short - this folder structure:

1) /mnt/web0/00/00/1234567/htdocs/2020-opencart/'
2) /mnt/web0/00/00/1234567/htdocs/2020-opencartstorage/'

So i did what the admin backend told me to do, and moved my storage folder outside of my shop root.
What confuses me now is that there seem to be several cache folders in my OC installation.

1. I have the "outside-root" storage folder mentioned above under 1).
2. I have another storage folder in 1) /mnt/web0/00/00/1234567/htdocs/2020-opencart/system/storage
3. I have an cache folder in images/cache

Is this all correct like that? As my "Image manager" stopped working again, i am a bit confused about so many cache folders.

Does there exist in the documentation or somewhere else something like a "folder-overview" ?

Find answers on such here, it has been Part of many Topics already:
viewtopic.php?f=202&t=206859&p=733949#p733949
https://www.google.com/search?q=Opencar ... +structure

The point to moving the Storage folder outside the public webspace is so it's not readable by the public.

If your storage path is
and you can publicly access
then it's pointless.