Credit card from revolut, what are the benefits?

Hello everyone, had to get a credit card recently as I need it to rent a car for a holiday I’m going on. Just wondering what the benefits are for a credit card? Do you get cash back or anything like that?

Also, when paying off the card it says it need to be fully paid off by the end of the month but what if I buy something that day or the day before will interest then be charged on that?

For context, I live relatively comfortably so outside of any big major expenses I should be fine to pay it off every month