Calls and Puts in Plain Words
There are only two kinds of options. A CALL is a bet (or booking) that a price will go UP. A PUT is a bet that a price will go DOWN. That's it — every strategy in the world is just calls and puts combined.
Options come in exactly two flavours: calls and puts. Get these two straight and the entire rest of the subject is just combinations of them.
A call = the right to BUY (you want the price up)
Buy a call when you think the price will rise. It locks in a buying price (the strike). If the market climbs well above the strike, your call becomes valuable because you can 'buy cheap'. If it doesn't, you lose only the premium you paid.
A put = the right to SELL (you want the price down)
Buy a put when you think the price will fall. It locks in a selling price. If the market drops well below the strike, your put gains because you can 'sell high' into a falling market. Again, your loss as a buyer is capped at the premium.
The Indian context
In India you mostly trade options on indices like NIFTY and BANKNIFTY, and on big stocks like RELIANCE. They trade in fixed bundles called 'lots' (e.g. one NIFTY lot is 65 units), and they expire on set dates (weekly and monthly). More on that next.
Go deeper — the technical detail
Each option also has a 'side': you can BUY (go long) or SELL (go short / 'write') either a call or a put. That gives four basic positions — long call, long put, short call, short put — with very different risk profiles, covered in Buyer vs Seller.