Whatsapp: where it stores media/macbook/icloud

Hi Guys, first time here:-)

Question:
I have been using WhatsApp on my iPhone for years. Recently purchased a MacBook.
Since I also use iCloud, it makes sense that the photo library on the MacBook is also in sync with the one on my phone.
Now I also see a (automatically created) WhatsApp folder with pictures in it on my macbook in my photo section.
However, what I can't figure out right away (and whatsapp don't provide decent feedback):

The photo library on my MacBook contains all the photos I take/recently deleted etc. on my mobile phone = clear (when in sync).

The WhatsApp folder on the mac does not contain all the photos which I see in my WhatsApp on my phone? Some pictures can clearly be found in a chat on my phone, if I compare by date and time on the macbook in the relevant folder, I can also see them in a relevant chat on my phone.
But this seems to be not applicable to all photos? Or does it also still store pictures from deleted/hidden/archived chats?
It also seems pretty clear to me that this whatsapp folder only contains sent photos? Due to settings in whatsapp (not to save received media)?
And is it possible that some of the photos in this Whatsapp folder are not in my default photo library? Should expect they are.
Should all photos in this WhatsApp folder be related to a chat? Or can they also end up here differently?

Anyone have an idea of ​​the difference and logic what is used here?

Thanks,
J