You can create lines that appear between a placemark and the ground. Of course, this line only appears if the placemark is elevated above the Earth.
To do this, first create a placemark. In the New Placemark dialog box, enter an altitude value above zero or use the slider and check Extend to ground.
Polygons, lines and paths can also extend to the ground. With these items, Google Earth draws a geometric shape from the earth's surface to the item.