A function has three general tasks it can perform; it optionally takes an input, does some processing and optionally ... To do that, I'll need to use a variable in that string somewhere. You can see ...

A function is a way of describing what happens to an input variable, in order to get the output result. \(\text{Input} \rightarrow \text{FUNCTION} \rightarrow \text{Output}\) If we think of a ...