Some function parameters (e. g. Graphics.DrawPicture(Image As Picture, x As Double, y As Double [,destWidth As Double ] [, destHeight As Double ] [, sourceX As Double ] [, sourceY As Double ] [, sourceWidth As Double ] [, sourceHeight As Double]) contain square brackets.
What is the meaning of these brackets and what is the usage? I cannot find any definition of this ‘feature’. (I just know hat they work)