A hand can be seen by the Leap Motion Controller. When AeroMIDI sees a hand, it displays it like the following.
This shows a hand object, also referred to as a tracker. In this case, it is showing the number five, which indicates that it sees five fingers on the hand. Hiding the number of fingers or obscuring them from the view of the Leap Motion Controller will reduce the number of visible fingers.
If the hand is showing fingers, it will look like the following.
This image above shows two hands with five fingers each. The left hand is colored blue and the right hand is colored red.