Did you ever wonder why Google has only one search box? You say, "why no - doesn't it work easiest that way?" Although secret, the algorithm that Google scientists use simply trolls through the mass of sites -every word and every site. But NOT really -- here are the key facts:
1. No search engine, not even Google, indexes all Internet websites.
2. Even Google does not index every page, screen, or word in a website that it indexes.
3. Given its new policies on advertising, some sites are offered some placement options.
4. Google treats every word equally - in other words, the searcher (that's you) is the one that determines whether or not the results are good. Google can't read your mind and you are not asking Google a question. You are simply searching for words.
5. Google does not charge you - right? That means that the pop-ups and little ads are its means to revenues.
So, what about what's missing from above and/or what if I am missing something?
1. For sites that contain data, articles, pictures etc. that have value and people pay for - these will not be found in a Google search. You would have to subscribe or belong to an institution that subscribes.
2. All of the public library databases, college library databases, institutional archives etc. are NOT included in Google.
3. Many sites contain sets of data stored in a database that requires you to do a second search, to use its search engine on its page in order to find and use the data. This is sometimes referred to as the grey web. It is not in the open, free area of Google, but is is not locked behind doors as is the pay-per-view stuff mentioned above.