The Sensebaord units with built in IMU (Inertial Measurement Units) can register the hand movements. Units with finger sensors (based on EFS) can measure the distance to the nearest part of the finger to the sensor.
When the Senseboard is put in gesture recognition you start a gesture by pressing the thumb-button. In a series of movements, the sensors registers these movements and can recognize your actual gesture. A separate software allows you to teach the Senseboard new gestures.