Continuous and discrete aren't concepts that are unique to Tableau. Indeed, both can be observed in many arenas. Consider the following example:
The preceding diagram is of two rivers: River-Left and River-Right. Water is flowing in River-Left. River-Right is composed of ice cubes. Could you theoretically sort the ice cubes in River-Right? Yes! Is there any way to sort the water in River-Left? In other words, could you take buckets of water from the bottom of the river, cart those buckets upstream and pour the water back into River-Left and thereby say, I have sorted the water in the river? No. The H2O in River-Left ...