Imagine a library with no front desk, changing shelves and new books arriving every second. Some books are locked. Some have no title. Others are copies with different covers. Finding the right answer in that library would be hard.
Search engines do some of the work of a librarian. They discover pages, study what they contain and decide which ones may help with a question. Your job is to make your business's useful information available, clear and dependable. You do not need to know the librarian's secret filing system to label your book well.
Three different steps
Crawling means fetching a page. A crawler is software that visits web addresses. Links from known pages and sitemaps can help it discover other addresses. Indexing means processing information for a search engine's collection. Serving results means selecting useful material when someone searches. These steps are related, but none guarantees the next. [Source 1]
A useful way to remember the difference is door, shelf, answer. Can the visitor reach the door? Has the library added the book to its shelf? Is that book useful for this question? A working door does not prove the book is on the shelf. Being on the shelf does not mean it will be chosen first.
Follow one fictional customer
Maya runs a fictional bicycle repair shop. Her homepage loads, but the repair page has no link from any menu or article. Someone who knows its exact address can open it. Other people may never find it. Maya adds a clear link from her services page because repairs are a real service customers ask about.
That is a discovery improvement. It is not proof of indexing or a higher ranking. To investigate those later steps, Maya needs the relevant search provider's reports and observations. If the report has not updated, the honest answer is still unknown.
Your first small record
Write down your homepage, main service or product page, contact page and the page where a customer takes action. Open each in a private browser window. Note what you can see without signing in. Do not assume that a page visible in your editing account is public.
Keep the stages separate: reachable, indexed and chosen are three different findings.