See the rest here:
http://www.ext.vt.edu/departments/envir ... agnum.html
More information here:
http://www.ipcc.ie/infosphagnum.html
So, "peat moss" could be the bog soil while "peat sphangum moss" could be the actual moss plant. I haven't run into "peat bricks", but I have run into bricks of the actual moss. Most things just labeled "sphangum moss" are the actual moss.
Hope that helps,
Marcos