Search engine spider or crawler is a Decision-maker Internet Bot. It takes decisions which website is providing best answer for a certain Google Search or any Search. It is one kind of programmed software which visit every single webpage exist on the internet after a certain time period. This Programme visits each and every single page and read all the readable content of a website.These bots are programmed such a way that they can understand the information of a website is providing.
It visits our website page sources. They follow some basic guidelines like they observe an article title if the title is mentioned HTML tag
Likes Headline Tag <H1>
Subcategory as <H2>
Its also read website
And Internal Links
By combined all these types of aspects and take a decision and give it a priority to rank in Search Engine. If a website is managing all the following guidelines then they have better possibilities to rank in Google or Search Engine.
We can stop search engine to crawl our site by declaring “Noindex” tag. So, Search engine spider will not crawl the page.
And One important thing. If crawler understands that you are misguiding its and trying to fool to rank on Google or search engine. Then they may “Deindex” your website. which means, your website will not appear on any search result EVER yes EVER. SO, this particular site has not valued at all.