Biofeedback is the process of gaining greater awareness of physiological functions using instruments that provide data or feedback on the activity of those systems.
With practice and awareness, users can learn to manipulate or control them at will. Some of the processes that can be controlled include brainwaves, muscle tone, skin conductance, heart rate, and pain perception.
Biofeedback may be used to improve health, performance, and the physiological changes which often occur in conjunction with changes to thoughts, emotions, and behavior. Eventually, these changes may be self-maintained without the use of extra equipment, although equipment is not necessarily required to begin practicing biofeedback.
Further Reading:
Using Biofeedback at Home – Personal Biofeedback Devices
What does a biofeedback machine do?
Biofeedback vs. Neurofeedback: What’s the difference?