By selecting this Tool, the following images appear on the Options Panel :

This is the Magic Wand Tool, which is so popular in other programs. It lets you make selections according to the objects color. The third option you have is the following:

It allows you to select polygon shapes.

Pen Tool:

creates polygons (and moreover straight lines, rectangles...) in a simple way. Many people find this tool to be complicated, although it's one of the most powerful tools that Flash provides.  .

Subselection Tool:

This Tool complements the Pen Tool, as far as it lets us move or adjust the vertices that make up the objects created by the above mentioned tool.

Ink Bottle Tool:

It is used to change quickly the color of a stroke. It is applied to objects with borders, changes the color of the boundary with one click in the Colors Mixer Panel.

Eyedroppers Tool:

Its mission is to "Capture" colors to use them afterwards.