InDesign offers a number of ways to wrap text around objects. You can wrap around an entire object container, around the edges of your placed object, or even select an alpha channel (transparency) of a placed Photoshop file. It's quite handy not having to draw another shape and fill it with "none" just to wrap text.

However, Anne-Marie Concepcion at InDesign Secrets points out something you must watch-out for when using the transparency of a placed object to wrap your text, and how to quickly fix it, in this article titled Making dynamic text wraper permanent.