Explanation

The XIP package contains the Wiki UI and can be used in case you want to continue the installation of XWiki offline. 

After installing XWiki using one of the available installation methods, your wiki is initially empty, meaning it does not contain any wiki Pages. Since applications in XWiki are implemented as wiki Pages, no applications are available at this stage. As a result, the Extension Manager (which is itself an application used to install extensions) is also not yet available. The XIP package allows the Distribution Wizard to find the necessary extensions locally instead of downloading them from the internet, making it suitable for offline installations of XWiki.

If, after installing XWiki, you want to continue the setup offline, you can install the XIP package. This package provides an offline extension repository that includes the Standard Flavor and all of its required extensions.