Brain wave frequencies explained...somewhat

It has  all to do with your neural oscillation, or as it is more commonly known – brain waves – which
naturally occur in 4 frequencies.

The most rapid brain waves, beta waves are generated when we are in ordinary waking state;

..when we close our eyes and become relaxed or unfocused, brain wave activity slows down and we produce alpha waves,

and as we become even more profoundly relaxed we may enter a somewhat trancelike state which produce a very slow brainwave called theta waves;

..the slowest of all produced in a state of almost unconsciousness, deep sleep, coma like,  has been labelled delta waves.

Brain Wave Frequency (cycles per seconds)
Beta Your natural, waking rhythm. Perception of all 5 senses and of time and space.	Alpha Experienced during light sleep. Higher intuition. The dream state.	Theta The level associated with deep sleep and relaxation. The mind remains active.	Delta Deep dreamless sleep also known as slow-wave sleep. Complete loss of body awareness.