A mile is a unit of length. There are many different kinds of mile but mile on its own usually means the statute mile.
The nautical mile is used for sea or air travel.
The nautical mile was originally defined as one minute of arc along a line of longitude of the Earth. There are 60 minutes of arc in one degree or arc (60' = 1°). So there were 10,800 nautical miles from the North Pole to the South Pole.
Now the nautical mile is defined as 1,852 metres.
1 nautical mile = 1,852 metres (by definition) ≈ 6,076 feet ≈ 1.151 statute miles
The speed of a ship that travels one nautical mile in one hour is called one knot
The mile was first used by the Romans. It comes from the Latin phrase mille passus (plural: milia passuum). This means "one thousand paces". A pace is the distance each foot moves when taking one step.
1 Roman mile = 1,000 Roman paces (by definition) ≈ 1,479 metres ≈ 4,852 feet
Different miles have been used throughout history in various parts of the world. In Norway and Sweden, for example, a mil is a unit of length which is equal to 10 kilometres.