Could someone explain this code?

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Sanctus

	Method render()
	
		Local drawY%, drawX%
		Local tOffY%
		Local gOffX%
		Local actualDrawX%, actualDrawY%
	
		For Local y% = 0 To Height - 1
			tOffY = 0
			
			For Local x% = 0 To width - 1
				drawX% = x
				tOffY:+ 15
				
				actualDrawX% = (((((((drawX * (TILEWIDTH + 2))) - ((TILEHEIGHT + 1) * x))) - (gOffx))) - x) + offsetx
				actualDrawY% = (((drawY * (TILEHEIGHT + 1)) + tOffY) + (y * (TILEHEIGHT / 2))) + offsety
						
				If actualDrawX < 0 - TILEWIDTH Or actualDrawY < 0 - TILEHEIGHT Or actualDrawX > GraphicsWidth() Or actualDrawY > GraphicsHeight() Then
					' // Dont render if the tile is off screen
				Else
					If tile[x , y].blocked Then SetColor 255 , 0 , 0
					DrawImage (floorImageSet, actualDrawX, actualDrawY, tile[x, y].floorStyle)
					SetColor 255, 255, 255
				EndIf
				
			Next
			
			gOffX%:+ 30
			
		Next
		
		For Local point:TPoint = EachIn pointList
			
			point.SetOffset(offsetx + (TILEWIDTH / 2), offsety + (TILEHEIGHT / 2))
			point.render()
			
		Next
	
	End Method

As you see its the drawing part of a isometric engine...
So could someone explain for wath is each variable
Oh and and the to DiabloGames for suplying the free sourcecode
I'm trying to make my own isometric engine and I know some pinciples but I can't figure out this one