In practice
site: with a path gives a fast read on whether a section is indexed; intitle: and inurl: find template problems across thousands of pages.
Treat the counts as indicative. Search Console is the source of truth for coverage.
Why it matters
They are the quickest way to sanity-check an index problem before opening a crawler.
They also surface content you did not know was public — staging URLs, internal PDFs, exposed parameters.
Related terms