Who says it is? Totally black means that in the direction that you're looking (and each cell at the back of your eye adds up the light from a tiny cone of the sky) there's nothing at all shining. Of course there is stuff there, it just isn't very bright. Every little bit of dust in the solar system reflects sunlight (just not much of it), as do asteroids, comets, moons, and other planets. Also, there are billion of stars inside the cup of the big dipper. It's just that they're so far away you can't see them without a telescope.

Why can a telescope see what you can't? Because the telescope has a much bigger eye than you, and lets in more light from the small angle in which it's looking. But even a telescope can't see if there's too much light pollution from the nearest city... in that case the sky is too "grey" to see the distant stars.

So here's a question for you to investigate: How dark is "black"? Ever notice that after a few minutes of stargazing you see stars where you thought it was completely dark? Your eyes adjust, right? So how faint does a star have to be so that you can't see it no matter how long your eyes adjust?

In order to see something, it either has to shine like a star or reflect light like a planet.If you don't see either things happening, you see black--the absence of light.

I think the way to think about this is to consider how our eyes work. We see things because "visible" light is reflected by or emitted from objects, enters our eyes and is interpreted by our brain. What do we see if there is an absence of light?

Well, actually the absence of light causes it to be dark. Light is produced in stars; this light can reflect off objects. It is bright at the surface of the earth because the sunlight bounces off the rocks, trees and water and scatters the light. But in deep space where there are no large objects, there is nothing for the light to bounce off of. The overall density of stars in space is quite low; most space is empty like a vacuum.