Final answer:
The two key aspects of working with functions, besides the function header, are the parameters (inputs to the function) and the body (the code that executes).
Step-by-step explanation:
Aside from defining the function header, the two key aspects of working with functions are parameters and body. Parameters are the variables listed as part of a function's definition and act as inputs for the function, allowing you to pass data into the function. The body of the function is the block of code that executes when the function is called, and this is where the logic of the function resides. For example, in a function designed to calculate the square of a number, the parameter would be the number you want to square, and the body would contain the code to multiply that number by itself.