Transparency Arrows let you control graduated transparency. The direction and length of the arrow directly control the direction and extent of the graduated transparency. The arrow has handles at either end which can usually be selected. The transparency set by the slider in the Transparency Tool Infobar is applied to the selected handles.

If you don't want to see transparency arrows when dragging, press TAB when in the Fill Tool or Transparency Tool.

For more details on Transparency, see the Transparency Overview.