Well, that depends on who you ask. In today's society, the terms are used interchangeably. There was a time that there was a physical difference in size and weight of the units, but not really anymore.
As a computer industry, we usually use the term NOTEBOOK more just because we don't recommend using them on you lap. The biggest reason is that when you place a notebook on a soft surface (like your legs, on a bed, on a couch) the unit presses into the surface, commonly blocking the heat vents on the bottom of the unit. This can cause issues from simply allowing the unit to run hot which can slow it down, to in extreme cases the heat can damage the computer or burn your legs!