CVector2D is external class which I've written to help out with positioning (among other things) the object in the game. So in my code I have several CVector2D objects holding the player's (the turret's) position, size and such.
The DeltaTime varible is a float (decimal) variable that is passed to the update function, which holds the time between the current frame and the previous frame. By multiplying the position update with this variable, I get the same speed on different computer, since I don't want the game to run faster/slower on a faster/slower computer.
The -> keyword/prefix means it's a pointer to something. In my case, I have a pointer to an InputManager class object, and whenever I want to call a function (or something else) inside that class object, I need to write InputManager->, followed by (for example) a function name, in my case 'KeyHeld'.
The 'f' prefix in some of my variables means it's a float (decimal) value. For example, when I write 'CVector2D(200.0f, 200.0f)' I set a vector's x-position and y-position to 200.0f, which is a decimal value of 200.0, and I insert an 'f' afterwards to let the compiler know it's a float value and not a double value (which it is without the 'f' prefix).
Whether to use 'void' as a function parameter or not is up to the programmer, since it's only a matter of personal taste. I always insert 'void' in a function without any parameters to note that it's a function without parameters.
This means that 'MyFunction(void)' and 'MyFunction()' does the same thing.
And finally, here are some links to information you might need to read up on:
Linear algebra + vectors:
Deltatime (sorry for the awful choice of background color vs text color):
I will post a simple 2D vector class below, which you can just add to your project and use.
Don't forget to add #include "CVector2D" at the top of your project when you've added the new class and wish to use it.