Essentially, the basic job of a search engine is “information retrieval.”
Ask a question, get an answer.
Seems simple enough.
The science behind getting search results is called the “algorithm.”
A search for “invention” will present you with definitions and perhaps lists of inventions (search engines have discovered that people love lists).
A search for “19th century inventions” will present you with mostly lists.
An American search for “inventors” will give you lists that include names like Thomas Edison, Nikola Tesla and Alexander Graham Bell.
If search engines existed 200 years ago, the results for an inventor search would probably include Ben Franklin, Leonardo Da Vinci and Archimedes.
Of course, those results are based in the United States. In France, or almost any other country, the results could be very different. Our own perception, and knowledge base, influences what we expect to see, and what the end results of a search will bring us. The Google Algorithm takes these influences into account.
The Google Algorithms consider keywords, related keywords, classifications, location, query intent and the hyper-focused user intent.
You don’t necessarily always get the same result. Do a search from a ‘clean’ computer, not affected or tarnished by your previous searches – not signed in – , a new location, a different browser, different i.p. and you’ll probably see different results. You may learn something new.
Seasons, your location, your prior searches, and regionally spiking searches effect results. If a local radio station asks a question for a contest, it will nudge results a bit. If a nationwide event occurs, with thousands or even millions of searches for a term or phrases, it can change the results significantly, temporarily or long term, if the algorithm decides.
Google is always learning, and giving educated guesses. Search Engine Optimization is the science (we call it an art) of keeping track of what you see, the data search engines have, and what Google thinks you are looking for.
Next time you do a search, along with your results try: Google Suggest, People Also Ask or Related Searches for a different perspective on the answer(s) you are looking for.