What is meant by an instance?

Answer
Java:
In Java an instance refers to an object of a particular type. For example ArrayList lst = new ArrayList();
now lst is an instance of type ArrayList. You can create instances of all possible objects and data types.

Answer
/* Let's say that we code a class called Shape: */

class Shape
{
private:
int m_area;

public:
int getArea(){return m_area};
void setArea(int area){m_area = area};
};

/* To use this class we must create an object, which is an "instance" of this class */

int main()
{
Shape x = new Shape();
Shape y = new Shape();
Shape z = new Shape();

/* We have created 3 objects (x, y, and z), each of which is a separate instance of the Shape class, we can now manipulate these objects: */

x.setArea(5);
y.setArea(7);
z.setArea(120);

cout << "Area of x is " << x.getArea() << "\n";
cout << "Area of y is " << y.getArea() << "\n";
cout << "Area of z is " << z.getArea() << "\n";

return 0;
}