Words used here

These are the terms that recur across the notes, defined the way they are used on this site. Each one links to the note where it is worked through properly.

Canonical: The address you declare as authoritative for a document that can be reached in more than one way. Explained at length in One page, four addresses: duplicates and canonicals.
Click depth: The smallest number of links that leads from the homepage to a given page. Explained at length in Internal links are plumbing, not decoration.
Crawler: The program that requests addresses, reads what comes back, and adds newly found addresses to its queue. Explained at length in How a crawler decides what to fetch next.
Impression: One appearance of your listing on a results page that was shown to somebody. Explained at length in Reading your own traffic data without fooling yourself.
Index: The stored collection of pages that a search engine has kept and may return for a query. Explained at length in What indexing actually decides.
Noindex: A directive inside a page or its response headers asking that the page not be listed. Explained at length in Robots.txt and noindex are not the same instruction.
Orphan page: A page in your site that no other page links to. Explained at length in Internal links are plumbing, not decoration.
Robots file: A public file at the root of a host naming paths that co-operating crawlers agree not to request. Explained at length in Robots.txt and noindex are not the same instruction.
Snippet: The descriptive text drawn under a listing, assembled for the query that produced it. Explained at length in Description text, and why snippets ignore it.
Soft error: A page that reports success while telling the reader that nothing was found. Explained at length in What indexing actually decides.
Title element: The single line naming a page, used in result listings, browser tabs and shared links. Explained at length in Writing a page title that survives the result list.
Zero-click query: A question answered on the results page itself, so no visit to a site follows. Explained at length in Twenty years of the results page.