Hulless barley is free threshing (the grains are easily detached from the glumes), while most barley varieties are hulled. Hulless barley was grown a lot in ancient times, but later hulled barley took over, though hulless barley was still grown here and there. For small scale growing hulless barley is practical, since it is easier to extract the grains.
Intermedium barley is a term for various kinds of halfway variations between two-row and six-row barley. The most common are six-row varieties that only have awns on the middle grain of each spikelet, and where the side grains are awnless.