With every transaction on Credit Card you get Bonus Points which you can redeem for free gifts or sometimes in cash equivalent (Its true... long back when lifetime free was not a norm, my Dad once paid his annual fee with the help of Credit Card bonus points).
This reward point structure varies from Bank to Bank. Sometimes it is flat and sometimes it depends on your transaction volume. The more points you earn, the more gifts you can redeem.
Sometimes, apart from reward points, now a days you can also get cash backs. Card companies are advertising a lot about 5% assured cash back on any transaction. This may have certain catch (read the fine print) but sometimes you can actually get certain cash back for filling petrol from particular petrol pump (and swipe on a machine from a particular bank) or shopping from a particular super shop. The fine print here is regarding a maximum cash back capped at 500 Rs or it is 5 reward points for every 100 Rs spent.
This cash back and Reward Points are definitely a plus of using Credit Cards.