What is theta decay and why does it hurt option buyers?

Theta accelerates as expiry approaches. An option with 30 DTE loses much less time value per day than one with 5 DTE. As a buyer, give yourself enough time — avoid buying options close to expiry.

Yes. Theta is time decay — every day that passes, option loses some value even if the underlying stays flat. This is why being an option buyer requires the stock to move quickly in your direction.