When you insert any of the shapes available in PowerPoint, you are not limited to what their default appearance looks like. You can change a rectangle to a rhombus, or even edit a curved or freeform line differently. You can do this by using the Edit Points option — this almost makes PowerPoint a drawing program that provides you the option to play with vertexes (points), handles, etc. — very similar to what you would do in Adobe Illustrator. A vertex is a point within the outline of any shape that can be dragged or edited to change the appearance of the shape.
Learn how to edit the structure of a shape in PowerPoint 2011 using the Edit Points option.

