Tube is specified by its outside diameter. Tubing is normally "cold drawn" seamless with the O.D. the same as the size designation (i.e.: 1" (25mm) inch tubing has an O. D. of 1 inch (25mm)). Tube is OD x wall unless DOM (Drawn over Mandrel) which is technically OD & ID, DOM in SSID (Special smooth ID) is ID and Wall.
Pipe is specified by its nominal inside diameter and Pipe has a wider variance in wall thickness. Pipe is to the pipe charts as per SB's comments NPS and schedule. Pipe can be made off the "pipe charts" but the reality is the more generous tolerances vs tube and uses the NPS for the first designation. It gets a few wrinkles in welded vs seamless for tolerances. 1-1/2" SCH40 Pipe, the 1-1/2" is the inside dimension but the actual inside dimension might be 1-5/8" instead.
Pipe is made seamless or rolled and welded (sometimes referred to as ERW pipe) . The pipe sizes up to 12' has a nominal size which is close but not the same as the actual O. D. Pipe in sizes 14" and larger have an O. D. the same as the nominal size. Both the seamless pipe and the ERW pipe comes in different wall thicknesses depending on the pressure/temp criteria. Pipe normally comes in lengths called "single random" (20'+/-) or "double random" (40'+/-). ERW pipe is also furnished in very long lengths, spooled on large coils for pipeline needs. Pipe 2" (50mm) and smaller is normally joined by threading or socket weld. Pipe 3" (80mm) and larger is normally joined using butt weld pipe fittings.
In addition tube is usually flexible or bendable, whereas pipe is usually rigid.