Theta brainwaves occur in deep meditation.
Theta brainwaves are associated with deep relaxation and with some stages of sleep, including the lighter stages of non-REM (NREM) sleep.
Deep meditation produces theta waves, which are slower and of lower frequency (between 5-8 hertz) than Alpha waves.
Theta is our gateway to learning, memory, and intuition. In theta we are in a dreamlike state.