It can be safely said that most of our world solely relies on Google's and a few other search engine companies. Without them finding information on the web would be an unimaginable task. Search Engines read, memorize and store information about most of the normally available (billions) websites that are out there. I bet there are smarter than you and me combined.
SEO or search engine optimazion basically means that you format your website in a way that Google and its cousins like. You need this otherwise your website won't be taken seriously and won't appear in search results. A SEO rule of thumb is that you do your best to publish valuable content in a well-constructed website. Google demands a lot and these demands often change. It looks like we are in the hands of SEO nerds!