There are two types of Orchids....terrestrial which need soil to grow and include most of our native orchids and epiphytic orchids which use a host to cling to and get their nutrients and moisture from the large aeriel roots or taken in through the leaves.
Most supermarket orchids such as Phaelenopsis (moth orchid) produce thise big aeriel roots. Don't cut them off but give them a mist every so often. I wouldn't pot it either...most orchids like having their roots squashed up a bit.
have a look at this website
http://everything-orchids.com/