Cannot download Office files in SharePoint browser

Question

I have a user whose permission level to a certain subsite is customized.

I'm currently investigating about user permissions and I found out that the minimum permission in order to download a file in SharePoint browser is the View items permission.

However, downloading Office files (like docx, xlsx, pptx) gives me an Unauthorized Access error, so I investigated again and I found out that it needs the Open Items permission together with the View Items permission in order to download any kind of files (including Office files).

My question is: What is in the Open Items permission that make the Unauthorized Access error not occur in downloading Office files?

Or what is the Office files that makes an error when permission is only View Items?

Answer 1

View Items Permission

gives only view permission to the Items present in library like below. therefore you can see the name of file only.

Actual file is associated with the name and for that

Open Item permission

is required.