System.Drawing namespace provides the most important classes for drawing.

Class
Bitmap
Brush
Brushes
ColorConverter
ColorTranslator
Font
FontConverter
FontFamily
Graphics
Icon
IconConverter
Image
ImageAnimator
ImageConverter
ImageFormatConverter
Pen
Pens
PointConverter
RectangleConverter
Region
SizeConverter
SolidBrush
StringFormat
SystemBrushes
SystemColors
SystemFonts
SystemIcons
SystemPens
TextureBrush
ToolboxBitmapAttribute

Structures

Class
CharacterRange
Color
Point
PointF
Rectangle
RectangleF
Size
SizeF

Point and Size and Colors are used to position form elements within the form. It’s used in many different ways. Here are several examples how it is done.
  button1.Location = new Point(10, 10);
button1.Left = 10;
button1.Top = 10;
button1.Size = new Size(30, 30);
button1.ForeColor = Color.Red;
button1.BackColor = Color.Blue; custom button1.ForeColor = Color.FromArgb(10, 200, 200);

In order to draw line you need to call Graphics object and then you’ll have several methods readily available to you such as:Clear, DrawEllipse, DrawIcon, DrawLine, DrawLines, DrawPath, DrawPie, DrawPolygon, DrawRectangle, DrawRectangles, DrawString in order to use this methods you must provide instance for the Pen class.

Graphics myGraphics = this.CreateGraphics();
Pen myPen = new Pen(Color.Red, 7);
myGraphics.DrawLine(myPen, 1, 1, 200, 200);

OR

Graphics myGraphics = this.CreateGraphics();
Pen myPoint = new Pen(Color.MediumPurple, 2);
Point[] points = new Point[]
    {new Point(10, 10),
        new Point(10, 100),
        new Point(20, 65),
        new Point(200, 100),
        new Point(95, 40)};
myGraphics.DrawPolygon(myPoint, points);

Pens can be customized in variety of different ways for example patterns and endcaps. You can also fill images or shapes using Graphics.Fill method.
Graphics myGraphics = this.CreateGraphics();
Brush myBrash = new SolidBrush(Color.Maroon);
Point[] points = new Point[]
    {new Point(10, 10),
        new Point(10, 100),
        new Point(30, 65),
        new Point(200, 100),
        new Point(95, 40)};
myGraphics.FillPolygon(myBrash, points);

 We can also draw a circle usingGraphics.DrawEllipse method.