Does 'indexable' mean 'will be indexed'?

No. It means nothing is stopping indexing. Google still decides based on quality, duplication and crawl demand.

Which robots.txt rules does it use?

The Googlebot group (or * if none), using Google's longest-match rule with Allow winning ties.

No. The server fetches the page the way an anonymous crawler would.

Analyzer

Fetch any URL and check the signals that decide whether Google can index it: status code, robots.txt, noindex, canonical and more.

Try:

The page is fetched by our server (it can't be done from your browser), analysed, and not stored.

Passing every check means search engines are allowed to index the page. IndexBoost helps them find it faster by submitting new URLs automatically.

Context

01
Noindex hides in two places
A noindex can come from a meta tag or from an X-Robots-Tag HTTP header. This tool checks both, because the header is easy to miss.
02
Blocked is not the same as noindex
robots.txt stops crawling but a blocked URL can still appear in results if others link to it. To remove a page, allow crawling and use noindex.
03
Canonical to another URL means 'index that one'
If the canonical points elsewhere, Google will usually index the other URL and drop this one. That's correct for duplicates and a bug everywhere else.