Add 'How It Works'

How-It-Works.md

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+FixPhrase.com uses an open source, patent-free algorithm to convert latitude and longitude into a set of four words from a word list.  Those four words (a FixPhrase) can be put back into the algorithm to get the original latitude and longitude.
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+FixPhrases can be shorter than four words too if less accuracy is required.  The first two words will locate a city, the first three words will locate a neighborhood, and all four words will locate the corner of a house, the pitcher's mound in a baseball field, or six adjoining parking spots.