Mile is a historical unit of length and commonly used in many measurement systems to measure the distance between two geographical locations. After metric system is accepted in many countries, it's replaced with kilometer but still used as an official measurement unit in united states, britain, canada and a few other countries world wide.
The "mile" used in this conversion page is the land (statute) mile. After the definition is changed in 1959, united states still wanted to use the old definition in some measurements and called it "US survey mile" which is only "0.0002%" longer (5280.01 feet) than the land mile. The other common unit "nautical mile" is used mostly in aviation and shipping and it's 1852 meters or 6076.12 feet. The abbreviation is "mi" (nautical mile is "nm" or "nmi").
Foot is another historical length unit (simply used as a body part) in several measurement systems. With the metric system, it's replaced with "meter" (british spelling is "metre") but still used as a very common lenght unit in united states, britain, canada and a few other countries. Similar to the usage of mile, foot has a few versions as well (international, survey etc). It's defined to be 0.3048 meters (12 inches). The abbreviation is "ft".