what is the difference between variable and member variable?

Simple! A local variable is the variable you declare in a function. A member variable is the variable you declare in a class definiton. Hmm... Still confused?

When we define a class, we can give that class member variables. These variables are members of that class. Take, for example, the following class declaration.

public class VanillaGodzila {
int a;
int b;
}

The class VanillaGodzilla has two member variables, a & b. When we define an object instance of VanillaGodzilla it will still have two member variables, a & b. We can reference these members using the '.' dot character.

// Create an instance of VanillaGodzilla

VanillaGodzilla obj = new VanillaGodzilla();

// Assign new values to a & b

            obj.a = 1;
            obj.b = 65536;        

These variables belong to VanillaGodzilla, and are known as member variables. On the other hand, if we declare variables inside of a function, we call these local variables. These variables are local to a particular function, and not publicly accessible.

For example, in the following function, we have no way of accessing the obj variable outside of the main (String[]) function.

public static void main (String args[]){

        VanillaGodzilla obj = new VanillaGodzilla();

        System.out.println ("A" + obj.a);
}

I have struggled quite a lot before I had it crystal clear and hopefully this helps. Best,