1.Drill pipe is hollow, thick-walled steel piping that is used on
drilling rigs and horizontal drilling to facilitate the drilling
of a wellbore and comes in a variety of sizes, strengths, and
weights but are typically 30 to 33 feet in length. They are hollow
to allow drilling fluid to be pumped through them, down the hole,
and back up the annulus.
2.Drill pipe is a portion of the overall drill string. The drill
string consists of both drill pipe and the drill stem which is
the tublar and the drill stem which is the tubular portion closest
to the bit or downhole assembly.
3.Drill pipe and drill stems can be differentiated in that the
drill pipe is quite flexible and produced in longer segments 
whereas the drill stem is much more rigid and manufactured in
shorter task specific segments