These are the different Pen option you will get once you click and hold down on the pen tool icon. There are 4 options to choose from, Pen Tool which is the normal tool, Add Anchor Point tool, Delete Anchor Point Tool and Convert Direction Point Tool it will also display there short cut key next to them.
The first tool from the list is the pen tool and this is the standard one you will see in the tools panel before this menu. As you can probably tell the short cut key for the Pen Tool is the letter P. The Pen Tool will let you draw straight and curved lines by clicking where you want the line to start then clicking where you want the line to end and then you could click back to the starting point to make a solid shape. These points you plot are called anchor points.
When you have decided where you want the end point click it but do not let go of the click. If you keep holding down you can drag the mouse around and you will see the Line start to curve. This is because you are editing the lines curve handles and each anchor point will have its own set of handles.
The next tool on the Pen Tool drop down list is the Add Anchor Point Tool. This tool is very simple and all you use it for is to add anchor points any line created in InDesign. When you have the tool selected hover over a line and you will see a plus appear next to the mouse this means you can add an anchor point. You will see that the short cut key for this tool is the equals sign.
Below you will see that I have added an anchor point to this line and have already started to edit the curve handles of the anchor point.
This next tool in the list is called Delete Anchor Point Tool and is the opposite tool to the Add Anchor Point Tool. This will delete the anchor point you have selected but in doing so it can alter the appearance of your shape.
This is the same line we added an anchor point to and now you can see we taken it away and it has gone back to the original line shape that will draw in the Pen tool demonstration.
The last tool in the drop down list is the Convert Direction Point Tool, anchor points in a line either will show a smooth curve or a corner. This tool will switch the anchor point between these to options.
I used this tool on the bottom anchor point and you can see it has made the line go dead straight in between the two anchor points.