I'm not sure what their policy is for people in India. You may not be approved. I would look into that before applying.
The Amazon Rewards Card is a credit card. If you want, you can apply for it, and use it only for that purchase and never use it again. Or you can use it only for your Amazon purchases. Or you can use it as your day to day credit card.
Every purchase gives you points, which you can use to buy more Amazon stuff.
As with any other credit card, I recommend buying only what you can afford, and paying the bill in full on or before the due date to avoid interest rate charges and late fees.
If you decide you don't want to use it any more, you can cancel the card. This will help make sure no one else uses it, and keep your credit report from looking like you have too much credit.
