https://www.healthline.com/health/alpha-brain-waves#different-types-of-brain-waves

What Are Alpha Brain Waves and Why Are They Important?
Medically reviewed by Heidi Moawad, M.D. — Written by Jennifer Larson on October 9, 2019
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So, while you’re warming up your muscles, your brain is producing alpha waves. You’re not asking your brain to process a lot of information or solve any big problems. The waves simply indicate that you are in a state of wakeful rest.

You may also be able to increase your brain’s production of alpha waves when you stop focusing or concentrating on a task, and simply try to relax and unwind.

Interestingly, a 2009 study suggests that your brain may produce even more alpha waves in the posterior part of your brain when you meditate. Your brain isn’t totally at rest, but it’s not attempting to tackle anything big that requires concentration.

… more … quick discussion of all other types of brain waves …