Your mind, your brain, your will, etc. Knowing the reasons behind the eightfold path, and knowing the mind states that are conducive to different workings may help you improve your magick. Understanding how and why you react to different situations is an important step in becoming an 'advanced' practitioner. Exploring your inner self will help you to gain this understanding and entering different mind states may assist you in your quest.
Alpha refers to the dominant brainwave pattern associated with a particular state of mind.
The frequencies fall into four categories that are present at all times in the brain. The dominant frequency is considered what 'state' you are in. Brainwave frequencies are measured in cycles per second or cps. This state is associated with wakefulness. It is the state you are probably in right now as you use your senses to take in information.