[Bf-funboard] Too many vertex lines

[hovergo at net-tech.com.au]

Hello all
I created a 4 mm thick sheet using cube (Thanks to edge measurements)
I created a cylinder through the cube sheet to drill a hole series of  
various sized holes in the sheet (cube).
In object mode, Select the sheet then the cylinder.
When using boolean operation in blender to subtract (difference) a  
cylinder from a cube I get a lot of extraeneous vertex lines and need  
to get rid of them.
How can these be removed without destroying the faces of th cube  (sheet)
Why doesn't Blender simply subtract one from the other as in real life  
like making a hole.
Why does blender create a new and unnecessary object set.
how does intersect, union and difference compare with add, subtract  and 
joining components, would I be correct in supposing that 'union  means 
add' and  'difference means subtract'.
Can someone help please.
thanks
Roger