Tubing isn't Pipe, and it isn't Hose
TUBING is sometimes similar to HOSE, in that it is sometimes flexible.
TUBING is sometimes similar to PIPE, in that it is often ridgid.
But TUBING is neither hose, nor pipe. The big difference is that tubing is sized by its Outside Diameter, but unlike Pipe (whose dimensions are controlled by its O.D., yet specified by its nominal I.D.), TUBING is specified by its actual O.D. (typically with tight tolerances).
Fitments for Tubing
Tubing is usually fitted with either a FLARE, or a COMPRESSION fitment, though there are exceptions, such as welding or brazing, for instance. There are many subtle differences among all of these fitments...