An option's price is split into two parts; the intrinsic value and the time premium. The intrinsic value is the amount the option is in the money. The time premium is the price of the option over and above the intrinsic value.
If you're trying to make your money by selling premium, that means your focusing on making money from the time premium decay of the option (theta). You may additionally be trying to make money on price movement and volatility changes, but that's not your main focus.
Understood, thank you. I'm not sure weather "selling premium" is an industry-wide term which implicitly refers to just the extrinsic value but I get very well what you mean. For me it's entirely irrelevant if I buy/sell an ITM or OTM option since it's only the extrinsic value that counts, all the rest being hedged away through a position of 1 or 0 in the underlier.
