When to use void (not returning a value) and when to use functions that do return a value?

I am pretty new to writing code and this is REALLY a basic question, so please, don’t butcher me! I just started learning C++ today on openFrameworks.

I am having trouble understanding why, and when do we use void where the function doesn’t return values, and when do we use functions that DO return values?

This will prompt others to say that it is a broad question that will inevitably draw a broad range of answers, so to make it specific, it would be helpful to use any basic scenario that you may think would illustrate the difference.

I suggest you some tutorial on C++, and maybe some time to make confortable with it, before coding with OF.
Here’s two starting point:
The latter is more OF oriented, but miss some basic feature of C++