When scientists first measured brainwaves they found that they were connected to different mind states, or states of consciousness. Since then they have divided the brainwaves into four predominant speed ranges, or types. The brain is constantly emitting nearly every type of brainwave. However, based on the strength of certain bands of brainwaves a person can be said to be "in" a certain brainwave or band.

Wave	Frequency	Mental State/Sub-Categories (bands)
Beta	15Hz - 38Hz	Individuals in this state are Fully Awake and Generally Alert.
Low Beta	15 - 20 Hz	Can increase mental abilities, IQ, and mental focus. High Beta (20 - 38Hz) – Can increase alertness, but may also produce agitation.
SMR	12Hz – 15Hz	SMR (sensorimotor rhythm) is related to body motion. Increasing this can result in increased focus, improved attentive abilities.
Alpha	8Hz - 12Hz	>Most people experience this state just after waking and right before sleep. This band is ideal for Relaxation, Stress Relief, Self Hypnosis, stimulation of the Immune System and Accelerated Learning.
Theta	3Hz - 8Hz	Most people enter into this state during light sleep or extreme relaxation.
Low Theta	3 - 5 Hz	This band is ideal for Meditation and Sleep Replacement. Additionally, research has shown that the suppression of this band can improve concentration and attention, as well as reduce hyperactivity.
High Theta	5 - 8 Hz	This band is ideal for Improved Sleeping Patterns, Treatment of Insomnia and Creative Visualization.
Delta	0.2Hz - 3Hz	This state is experienced during deep, dreamless, non-REM sleep. Delta is the slowest band of brainwaves. While in Delta the body is healing itself and resetting internal clocks. This band is ideal for Accelerated language retention and stimulating the release of growth hormone.