The Pen tool allows for completely freeform drawing on your chart, similar to drawing with a pen on paper. It creates a continuous line that follows your mouse movement exactly.
The Path tool creates a connected series of straight line segments. Unlike the freeform Pen tool, Path creates precise, connected straight lines between each click.
The Polyline tool creates an open-ended series of connected line segments. Similar to Path but designed for creating open shapes rather than closed figures.