Ground orchids are of the species
bletilla striata and are terrestrial, which means they thrive in soil versus the majority of orchids which are epiphytic using other plants/mediums as hosts to live on, although they derive their own nutrients through means other than their hosts; that is why most orchids roots tend to
stretch out into the air - to seek moisture to supply water and nutrients to the plant. In regard to the
ground orchid check out this link here:
Bletilla striata -- species description
And about the paph orchids, here's you yet another link for detailed information:
http://www.orchids.org/culture/paphiobeginner.pdf
I have found that entire site to be extremely varied in its information and quite helpful in ways more than one! Hope this helps and answers your questions