Within this very large group of plants, we find a number of Subfamilies, Tribes and Subtribes, that link together plants with similar characteristics--both plant and flower structure.
This can be quite confusing to many, so the graphic FTD has produced really helps to visualized the linkages between these different types of orchids. Here it is, in all its glory:
Produced by FTD.com.
Be sure to click on the image to visit the FTD blog site.