For which parts would you need to enter a credit card? The addons? I've used Heroku for some assorted Ruby and Python programs, but I have not had to enter a cr

For which parts would you need to enter a credit card? The addons? I've used Heroku for some assorted Ruby and Python programs, but I have not had to enter a credit card. However, what I have done has only scratched the surface of what Heroku offers, so I am not surprised if I missed the the parts that require credit card info.