The first category of brainwaves is beta. Beta brainwaves are the lowest in amplitude and the fastest of the four types. When the brain is actively engaged in an activity, it is displaying beta brainwaves.

The frequency of beta brainwaves ranges from 15 to 40 cycles per second. The 15 - 20 hertz (Low Beta) brainwave band is associated with super-focused concentration, better memory, and improved cognitive function overall.

The second category of brainwaves is alpha. Where beta represents arousal, alpha represents the opposite - non-arousal. Alpha brainwaves are slower and higher in amplitude. The frequency ranges from 9 to 14 cycles per second.

If you have just completed a task and sit down to rest, you would be in an alpha state. Meditating or taking a "time out" to relax and reflect would also put you in an alpha state.

The third category of brainwaves is theta.

Theta brainwaves typically have an even higher amplitude than beta or alpha, as well as a slower frequency. Theta's frequency is between 5 and 8 cycles per second.

You can think of your brain being in a theta state as a very positive thing. This state can occur when you are performing a task that is so automatic that you can mentally disengage from it - a repititious activity like brushing your hair, or a monotonous one, like driving on a sparesly populated highway. Going on your morning run can also put you in a theta state.

When your body can automatically perform a task without your brain having to be completely focused on it, this is probably a theta state. You may notice that you get a lot of ideas - your brain is able to free-associate and drift, coming up with all sorts of ideas and new angles you may have not examined before.

Delta brainwaves are the slowest in frequency of all four, and have the highest amplitude. They generally range from 1.5 to 4 cycles per second, though they never go down to 0, as that would indicate brain death.

When you are sleeping deeply, your brain is in a delta state. "Sleeping deeply" refers to dreamless, non-REM sleep. It is during this time that your body is healing itself, restoring itself, and resetting its internal clocks.

These are the four categories of brainwaves. Your brain is always in one of these states, whether you realize it or not. You can make use of these states to develop certain skills, such as using the theta state to plan the day's activities or using the delta state to enhance language retention.