Used These?: ply, dae, x3d

I recognize most of the imports/exports in Blender except these:

.ply: Created at Stanford University but what are the pros and cons?
.dae: Extended from XML (wiki). Is not that a markup language?
.x3d: It is the successor of VRML. That is as as far as I got with this one.

This might be an advance side question. How can the .ply format be used in ASCII or Binary. I have seen this stated. I had imagine ASCII only for text.