What it means
A crawler first needs to discover and fetch a page. The search system then decides how to interpret it and whether to keep it in its index. Being reachable, being indexed and ranking for a query are different things. Instructions such as noindex and canonical metadata help communicate the intended treatment of a page.
Why it matters to your business
Launch and preview settings must match the intended audience. A page can be public for review while asking search engines not to index it. Private information needs actual access control: a noindex instruction does not prevent a person with the URL from opening an otherwise public page.
Reviewing a site before search launch
A business opens a temporary public site for content review and keeps noindex on its responses. It allows crawlers to fetch the public pages so they can read that instruction. Removing noindex later is a separate launch decision, followed by checks of the real responses and canonical URLs.
Questions worth asking
Are robots.txt and noindex the same?
No. robots.txt addresses crawler access, while noindex asks a supporting search system not to include a fetched page. Blocking a crawler can prevent it from seeing the noindex instruction, so these settings need to be planned together.
Can we require a search engine to index a page?
You can make a useful page discoverable and check technical obstacles, but the search system decides whether to include it. Indexing also does not guarantee a particular ranking or how quickly search results will change.