What's the difference between a nautical mile and a statue mile?

I know the definition of both....and I know a Nautical mile is supposed to be 1852 meters...how do you figure the statue miles....I came up with a conversion of 47.25 feet per knot which gave me 1.07 miles but not sure if this is correct...also how do I come up with the 1852? My question I"m trying to answer says "One Nautical mile is the distance a ship travels in one hour if it travels at a speed of one knot for one hour. It is also the length of one minute of arc alon the Earth's equator. Using this, what is the cirference of the Earth in Nautical miles? The question before asks how many statute miles per hour is 1 knot? Then we have to use both of those answers to come up with the cirference of the Earth in statue miles....I just don't understand the difference between figuring the nautical and statute miles I guess...HELP?