Well consider a square like cell. The cell itself represents a certain object a class with different properties and methods. Now consider a rotating function.
Such function of a cell is able to rotate it's content for n degrees where n degrees is a function parameter.
The text's normal alignment is horizontal so by rotating it for 45° or -45° the new alignment is diagonal. By rotating 135° or -135° you also get a diagonal text but the problem is the text will be turned upside down which cannot be used.
Hope this helps.
r3t40.