Working of this pointer

You must understand that pointers are ONLY some memory address like a city address. And you must know what type of data or objects you may find there. Like the city address may be a house, a parking lot or only some bushes.
So when you have some pointers, you always need some data or object to which it points.
Some simple example:

int *pointer = NULL; // doesnt point to any object
int *pointer2 = new int;// points to some int memory
*pointer2 = 2;// fills that  int memory with a 2

For that reason it is best to ALWAYS work with typed pointers.

Read some good pointer tutorial to understand it.

Be very careful when casting pointers. It is a common cause for headaches and broken hardware.

this always refers to the current instance of the containing class.
Think of it as a car: you have your car, I have my car. If you put your mobile in the glove box of your car, you don't expect to find it in the glove box of my car because you understand that the two vehicles are separate instances of the class "car".

But ... you can also say "this car" and it can refer to any instance of a car: if you are pointing at your car then you would find the mobile, if you point at my car, you find a locking wheel nut key, a box of nitrile gloves, face masks - but no mobile.

It's the same with classes: this can refer to any class instance; you don't have to pass it to your function explicitly (in fact you can't change it) as the system sets it to the instance when you use the instance to call the function:

Car myCar;
Car yourCar;
...
myCar.OpenGloveBox();
yourCar.OpenGloveBox();

Inside the OpenGloveBox function you use this to refer to the specific vehicle, without having to know which one is being referred to.