That is because you are defining a variable to be passed to the loop function and the part of the code calling it ( this is hidden from you ) is not sending one.
No code you have seen in any of the examples in the IDE does that so why have you?
That is because you are defining a variable to be passed to the loop function and the part of the code calling it ( this is hidden from you ) is not sending one.
No code you have seen in any of the examples in the IDE does that so why have you?