Menue items define drawing objects, options for objects and other operations. Active menue items are displayed in inverse color (black). If you click with button 1 you can activate and deactivate items. If a new activation gets in conflict with other activations, then the other items are deactivated. Items may be active even when they are without influence to the current drawing process.
It is always(!) possible to click on a menue item to change an option or to abort an operation or drawing process. Menue items which are options are used at the latest possible point in the drawing process.