If you want your site to show up in the search results at all, then it needs to be indexed.
However, you don’t want your site to be indexed just once. You want the search engines to keep re-indexing your site.
Search engines like Google don’t just update automatically.
They rely on spiders — little bits of computer code that each search engine sends out to “crawl” the web (hence, “spider”).
You want an efficient, frequent crawl rate.
The spider’s job is to look for new stuff on the web and update the already indexed version of your site. That “new stuff” can be a new page on an existing site, a change to an existing page, or an entirely new site or blog.
