Rewards in India come in three shapes, and picking the right one is mostly a question of how much effort you are willing to spend.
Cashback is a percentage returned as money, usually as a statement credit and occasionally to your bank account. It is fixed and simple. A rupee of cashback is a rupee.
Reward points accumulate in a programme and are redeemed later for vouchers, statement credit, travel or merchandise. They are variable and flexible: the same point is often worth more against travel than against merchandise, and least against a catalogue of appliances.
Miles are points in an airline or hotel currency, either earned directly on a co-branded card or transferred from a bank programme. They have the highest ceiling and the most conditions.
Read the three gauges above as certainty, flexibility and ceiling. Cashback wins the first, points the second, miles the third — and for a first card, simple usually wins. But only after you have done the arithmetic in the next module.