Take the temperature, for example. Tell that to Mother Nature, pal. The temperature doesn't suddenly jump from 56 degrees to 57 degrees. It might be accurate enough to think of the temperature as being either 56 or 57, but we have to realize that we're just approximating it, just rounding it off. In fact, when you look at the way digital methods really work, they're always rounding things off.
Digital sound is like that.
Sound waves don't suddenly jump from one loudness level to the next, and yet the only way to record them digitally is to mark off the next level up or down the scale and attach a number to the sound level when that spot is reached. If you're thinking that this sort of chopped-liver attitude makes digital sound less than perfect, you'd be right. In some ways, digital methods are clearly best. And that big problem with digital sound doesn't apply to how well you can hear my voice over the phone, which is why Motorola and the other cellular-phone manufacturers digitize everything. But that's a technospeak kind of thing.