Compare Report - Keep Vanilla or Keep Customization

Compare Report
Why Keep Vanilla or Keep Customization ? What is the difference?
The following chart summarizes the various status, action, and upgrade possibilities that could be applied to a single definition during the upgrade compare process:

For example if the Source is *Changed and the Target is Changed, the ACTION will be COPY, but the Upgrade flag will only be YES (do the copy) if you have Keep Customizations selected. It will be NO if you choose PeopleSoft Vanilla and will not be copied.If you are seeing the Source and Target both as *Changed, it should copy in either case.
Now read the example above carefully. It means that, if the source is *Changed (customer modified) and the target is Changed (PeopleSoft modified), then in this case, If you select "Keep Customization" then the source object will get copied to target. But if you select "Keep Vanilla" then the customer's customized object in source will not get copied to target.