Generics

Well to understand generics let's consider this expample:
Say that you design a Rectangle class

public class Rectangle
    {
        public Rectangle(int height, int width)
        {
            this.height = height;
            this.width = width;
        }
        public int height { get; set; }
        public int width { get; set; }
        public override string ToString()
        {
            return string.Format("The height is {0} and the width is {1}", height, width);
        }
    }

You cloudn't define a new instance as bellow:
Rectangle Reg1 = new Rectangle(2.02, 2.05); since the height and width are type of integer you will recieve a compile error indicates that types aren't suitables

In the other hand, let's consider this class prototype

public class Rectangle
    {
        public Rectangle(T height, T width)
        {
            this.height = height;
            this.width = width;
        }
        public T height { get; set; }
        public T width { get; set; }
        public override string ToString()
        {
            return string.Format("The height is {0} and the width is {1}", height, width);
        }
       
    }
The user could precise the type of height and width by him self as so

Rectangle Reg2 = new Rectangle(2.02, 2.05);
            Rectangle Reg3 = new Rectangle(2, 3);
            Rectangle Reg4 = new Rectangle(255800, 25558221);
So there is no dependancy on a type you can precise the height and width type as you like

The generics are alomst used in lists and Ienumerable series