Basic distinction
Theta and alpha refer to neighboring ranges of oscillatory neural activity. Researchers define the exact boundaries somewhat differently, and both rhythms can appear across multiple cognitive and physiological contexts.
Why simple labels fail
Popular charts often map theta to creativity or meditation and alpha to calm focus. Those mappings can be useful mnemonics, but they are not deterministic rules. A person does not enter one uniform brain frequency like selecting a radio station.
For audio listeners
If an audio track is labeled theta or alpha, treat the label as describing the intended modulation/beat range. Whether that produces the advertised neural or behavioral outcome is an empirical question.