This discards everything after the host, leaving the bare domain. https://example.com/blog/post becomes example.com.
Changing what you are counting
Page-level data answers questions about pages. Domain-level data answers questions about sites. Stripping the path converts one into the other.
Where it is used
Backlink analysis, referral traffic review, competitor identification — all of which are questions about which sites are involved rather than which pages.
Deduplicate afterwards
Stripping paths creates many identical rows. The distinct count after deduplication is the number of sites involved, which is usually the figure that matters.
Try it: Strip URL Path (Keep Domain Only) on SeoWolf's Notepad.