Pipes are used for mass transfer eg- water pipes, steam pipes
On the other hand tubes are used for heat transfer eg -
superheater tubes, economiser tubes.
As per ASME section 2 part A the materials of tubes and
pipes are diferent. You can have pipes forged and rolled but
tubes are seamless. The tolerances on tubes are tighter as
compared to pipes so tubes are costly as compared to pipes.
Geometry wise there is no difference but differentiation is
based on the intended use.
From a layman's perspective.. Tube is a general term & pipe is a technical term. Tube can be anything even like a elect tube (Tube-light) or the underground-tube where the trains travel etc.. Pipe or 'Piping' is more related to application requirement & is regardless of ID/OD or length of the pipe.. hydraulic piping in M/c's or vehicles, Gas piping, water pipe's etc....