I am a teenager and i need help

I was looking at discounts to buy a gaming laptop on amazon and the best discount was on amazon pay icici bank credit card. After searching online regarding it, i found that it is different from a normal icici card. So what i understood is that we get a 5% cashback on amazon pay balance when we make a purchase from it for prime members and 3% cashback for normal members. So all i need to ask is whats the disadvantage?

Me and my family uses amazon a lot and a 5% cashback on all products would be really nice. After looking for it on the internet, i found that you dont get normal card benefits on things like rent and such. So why cant i just keep it purely for amazon?

Ps: i have little to no knowledge about credit cards in general. So dont hesitate to educate me.