So what does variables do? (In relistic situation)

Answer 1

A variable is essentially a memory location (literally an address in your RAM) that you give can a name and refer to by its name rather than its memory address.

int i = 0;

This line of code asks the system for a free memory location capable of storing a 32bit integer and assigns its value to 0.

I hope this helps.

Answer 2

They're used when you don't know what their value's gonna be (e.g. when using if or switch) or when you need to use some value often (e.g. content from a file, which you would otherwise have to read every time you need that data).

Look around on the playground and you'll see.

Answer 3

more information...

the framework predict when is possible free memory with GC (garbage collector), If the variable is not use on the context...