Pen Tool
The Pen Tool creates freehand notes and drawings in the 
Graphics View. This makes the Pen Tool particularly useful
when using GeoGebra for presentations or with multimedia interactive whiteboards. To add a freehand note onto a region
of the Graphics View, activate the
tool and draw using your finger or a pen (touch devices), or use a mouse while pressing and holding the leftbutton and releasing it when done (non-touch devices).
GeoGebra stores the note you traced in the Graphic View as a stroke object, to which it is possible to apply some actions and geometric transformations (e.g. move, rotate, reflect,…).
The default colour of the pen is black, but the pen properties (colour, style, and thickness) can be changed using the Styling Bar.
Erasing
To erase a portion of your note created with the Pen Tool in the Graphics View, select the Delete Tool and move your finger (touch devices) or the mouse pointer while pressing and holding the left button over the part you want to erase.
For non-touch devices it is also possible to erase part of a note by pressing and holding the right mouse button while moving the cursor over it and releasing the button when done.
To delete a pen stroke completely, select Delete in the Context Menu of the object in Algebra View or Graphics View.