Do you remember early computer programs/games/movies where someone asked the computer a question, and it gave the answer?
Well, that's no different today with search engines, and people use these search engines in the same ways...
People ask search engines their questions.
How to... what's the best... where to find... etc. etc. etc...
People use questions as search terms, and if you can master the art of providing the exact keyword phrases of the questions asked, you have a serious secret weapon on your hands.
Here's the Keyword Question tool I use:
Keyword Questions - Keyword Research Tool
Please share any other Keyword Question tools that you know of.