In air Combat, when an aircraft fires a missile at another aircraft, it is known as an Air to Air missile.

The Sparrows and Sidewinders were air to air missiles

An air-to-surface missile is a missile which is fired from an aircraft to the ground.

Surface to air is shot from the ground into the air at the target. Air to air is fired from another aircraft. Actually there is very little difference. just where the missile is fired from.
Of course, there can be many more surface-to-air missiles (SAM) than air-to-air (AAM) because an enemy aircraft can only carry a limited number.

The difference between a missile and a torpedo is that a torpedo travels in the waters and a missile flys through the air.

sam