Brainwave States

Frequency range	Brainstate Name	Associate With:
13-40 Hz	Beta waves	Alertness
7-13 Hz	Alpha waves	Relaxed but awake
4-7 Hz	Theta waves	deep meditation
<4 Hz	Delta waves	Deep dreamless sleep

The exact boundaries between ranges vary among definitions, and there is no universally accepted standard

The dominant frequency determines your current state. For example, if your alpha waves dominate, you are in the alpha state (this happens when you are relaxed but awake). However, also other frequencies will be present, albeit with smaller amplitudes. Gamma waves aren't usually your dominant frequencies.