A common question...
Assuming you're working through the tutorial in order, and you already know a little about functions...
A function can only return one variable. And, when you pass a variable into a function, you are passing-in it's value... not the actual variable.
If you want a function to affect more than one variable, you need to use pointers,* so that you can "get to" the actual variable.
Most programming books introduce pointers with a swap() function. The function swaps the values of two variables... Say X=2 and Y=4. You pass X and Y into a function that makes X=4 and Y=2. You can't do that with "regular" variables!
Pointers are also useful when working with arrays (lesson 8). Again, you can't return a whole array from a function, but you can get-around this limitation by returning a pointer to the start of the array.
* Actually uou could use references which are preferred 90% of the time in this situation.
