You are usin codecademy, right?
What is resources OP?

I have an old Arduino I´d like to use. But here the choice for this type of hardware is Raspberry.

I really do not know why these little motherboards are used in this context. Maybe just a matter of cost and space. I wonder if the Raspberry (or Arduino) is just a smaller or cheaper substitute for a computer. I have 3 computers and only use one, so I have a long way to go before arriving to the Arduino stage!