Calls and puts, from both sides
A call is the right to buy the underlying at the strike by expiry. A put is the right to sell at the strike. Each has a buyer and a writer, giving four basic positions:
| Position | You want | Max loss | Max gain | Pays / receives |
|---|---|---|---|---|
| Long call | Price up, fast | Premium paid | Unlimited | Pays |
| Long put | Price down, fast | Premium paid | Strike − 0 (large) | Pays |
| Short call | Price flat or down | Unlimited | Premium received | Receives |
| Short put | Price flat or up | Strike − 0 (large) | Premium received | Receives |
Notice the asymmetry. Buyers have small, known losses and open-ended gains; writers the reverse. Yet, as Chapter 6 will show, writers win more often — because buyers pay for that open-ended gain up front, and most of the time it does not arrive.
Moneyness: where the strike sits relative to spot
- In the money (ITM): exercising now would be worth something. A call with strike below spot; a put with strike above spot.
- At the money (ATM): strike closest to spot. Highest time value, highest gamma, the centre of the chain.
- Out of the money (OTM): exercising now is worthless. A call above spot; a put below. All of its premium is hope.
Look at the live chain. Read the CE column downward: calls get cheaper as the strike rises above spot because each one needs a bigger rally to pay. Read the PE column upward for the mirror image.
What the premium is made of
Every option premium is two things added together:
Premium = Intrinsic value + Time value
Intrinsic value is what the option would be worth if exercised this instant: for a call, max(spot − strike, 0); for a put, max(strike − spot, 0). It is never negative. An OTM option has zero intrinsic value by definition.
Time value is everything else — the price of the possibility that the option ends up (more) in the money before expiry. It depends on how long is left, how much the underlying tends to move (volatility), and how far the strike is from spot. Time value is highest at the money and decays to exactly zero at expiry. This decay is theta, and it is the reason option writing is a business.
Worked example on a live chain
Take the ATM row above. Say spot is 23,635 and the ATM strike is 23,650. The 23,650 call is 15 points OTM, so its intrinsic value is zero and the entire premium is time value. The 23,650 put is 15 points ITM: intrinsic value 15, and whatever the put trades above 15 is time value. You will find the call and put time values are nearly identical — they must be, or an arbitrage exists (that identity is put–call parity, and it is why the terminal's NET column, which measures the gap, hovers near zero).
Exercise, assignment and squaring off
In practice you almost never exercise an option in India — you square off: sell what you bought, or buy back what you sold, before expiry, and pocket the difference in premium. Exercise only happens automatically at expiry for ITM options. For index options that means a cash credit or debit. For stock options it means physical delivery, with its own traps (Chapter 9).
Your first mental model
Think of an option premium as rent on exposure. A buyer rents upside (or downside) for a period and pays rent up front; time decay is the rent being consumed. A writer is the landlord: collects rent, carries the building's risk. Neither is right or wrong — but you should always know which one you are, and what rent is being charged today. The next chapter teaches you to read that off the chain.