The mile is a unit of length in the imperial unit system with the symbol mi.
It was originally an English unit but was adopted by many countries who all had their own slight variation on definition. The English mile, however, is equal to 63,360 inches, 5280 ft or 1760 yards.
The UK still uses the mile on all roadway signs rather than the kilometre; its SI "equivalent". It used to have the symbol 'm' until SI was established and it was changed to avoid confusion with the unit metre.
The foot is a unit of length in the imperial unit system and uses the symbol ft.
One foot is exactly equal to 12 inches. It is also exactly equal to 0.3048m. One yard is comprised of three feet.
The foot is just behind the metre in terms of widespread use due to its previous popularity. The US is the only developed country that still uses the foot in preference to the metre.
The UK still uses feet to express human height more than metres.