Derivatives are contracts whose value is based on some underlying asset like a stock or index without actually owning that asset. F&O are two such types of derivatives.
A futures contract is an agreement between two parties to buy or sell the underlying asset at a specific price on a specified future date. This means both parties are obligated to complete the transaction when the contract expires unless the position is closed earlier.

Options work differently. In an option contract, the buyer gets the right but not the obligation to buy or sell the underlying asset at a predetermined price (called the “strike price”) before or on a given expiry date. That right comes at a cost known as the “premium.” The seller (writer) of the option, in turn, takes on the obligation, should the buyer decide to exercise.
Because options give a choice (right but not obligation), they tend to have a different risk-reward structure compared with futures or owning the actual asset.

Calls and Puts in Simple Words
Call Option
A call option gives you (the buyer) the right  but not the obligation “to purchase” the underlying asset at the strike price, before or at expiry. You choose a call when you believe the asset’s price will go up.
You must pay a premium upfront for this right. If by expiry the asset’s market price stays below the strike price, you can simply let the option expire, in that case you lose only the premium. 
If the market price climbs above strike price plus premium, you can exercise the option. The gain can, theoretically, grow as much as the price rises.
Put Option
A put option gives you the right but not the obligation “to sell” the underlying asset at the strike price, before or at expiry. You choose a put when you expect the asset’s price to go down.
Again you pay a premium to get this right. If by expiry the price stays above strike, you can let it expire, losing only the premium.
If price falls below strike by a good margin, you can sell at the higher strike price locking in a profit (after adjusting for the premium). The profit depends on how much the asset price has fallen.

Why People Use Options?
Options allow you to benefit from market moves while risking only the premium and not the full value of the stock or asset. Because the upfront cost is lower, this provides leverage compared with directly buying/selling the stock. 
If you own a stock already, options can act as a form of insurance. Suppose you want to protect against a possible drop in value then buying a put option can limit your downside while letting you hold the stock.
Options also provide flexibility. Based on your expectations whether bullish, bearish or neutral you can combine calls and puts in various ways to build strategies suited to different market conditions. 

What Beginners Should Know?
Buying a call or put option involves paying a premium upfront. That premium is the most you can lose if the market doesn’t move as expected. 
If you believe price will rise then consider a call. If you believe price will fall then consider a put. But always remember: option value depends on many factors not just price expectation, but also time until expiry, volatility, and how far the strike price is from current price.
Because options have expiry dates, time matters. If nothing happens before expiry, even a well-chosen option may expire worthless.
Options give a chance for big profits with limited risk, but also require discipline and understanding before entering. For many beginners, buying options (rather than writing them) tends to be a simpler way to start. 

Conclusion
Futures and options open paths beyond simply buying and selling stocks. With the right expectations and strategy, options allow you to benefit from price movements while keeping risk contained.