Here we go - definition of root beer:
Not really a beer! It was created in the mid-1800s by Philadelphia pharmacist Charles Hires, the original root beer was a (very) low-alcohol, naturally effervescent beverage made by fermenting a blend of sugar and yeast with various roots, herbs and barks such as sarsaparilla, sassafras, wild cherry, wintergreen and ginger. Today's commercial root beer is completely non-alcoholic and generally contains sugar, caramel colouring, a combination of artificial and natural flavourings (including some of those originally used) and carbonated water for sparkle.
Definition of ginger beer:
carbonated slightly alcoholic drink flavored with fermented ginger