system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 What are brainwaves and what’s the difference between for example beta and alpha waves?
gpt
brain waves are patterns we find in our neurons firing.  They're correlated with different mental states.  

alpha is associated with being awake but not really actively focused on anything.  It's what happens when you're awake, but you're not really focused in on a task.  These occur at about 9 to 14 hz.

beta is also associated with being awake, but it's correlated with active effort and concentration.  It typically occurs in bursts and is about 15 to 40 hz.

So basically if you're taking a walk in the park reflecting on the day you'd be in alpha.  Someone drops something that makes a noise you'll switch into beta for a short period of time as you react to that.  

Theta waves are between 5 and 8 hz and Delta are below 5 hz.  Both are associated with various stages of sleep.  Theta is associated with a "medium" sleep (stage 2 out of 5) while delta is associated with deeper sleep (stages 3 and 4 out of 5).