Hypothetically, if there was a substance that could absorb all visible light and reflected none, how would it appear to the human eye? Would said substance just be perceived as a "hole" in our vision, if it was capable of absorbing 100% of all light?
Also on a side note, would the absorption of all light instead of only visible light create any difference in this scenario? (I apologize in advance if this seems to be a pointless question, just looking for more insight)
 A: This substance would appear completely black. Also, if more than the visible light were absorbed, the substance would still appear absolutely black.
A: No material in the physical universe can absorb all radiation and emit none. This is only theoretically possible but not practically.  Not even black holes( they absorb all light but remember they emit Hawking radiation). But scientists have always strived to create a material that can absorb all radiation. The best they made was Vantablack. This material is made of vertically aligned carbon nanotubes ( hence the name). It can absorb 99.965% of light. If it is coated on any kind of material, because of its absorption you wouldn’t even be able to see the surface textures of that material. 
Even if any other frequency of light is absorbed, it doesn’t  matter to the human eye as you can only see in the visible spectrum.

You can find more on Wikipedia: https://en.m.wikipedia.org/wiki/Vantablack
A: Black body
100% absorption, 0% transmission and 0% reflection is the definition of a perfect black body.
Black bodies do emit electromagnetic radiation according to Planck's law, though, and aren't black in general.
A black-body at room temperature appears black, as most of the energy it radiates is infra-red and cannot be perceived by the human eye.
Magical substance?
If you meant to ask about a substance with 100% absorption, 0% transmission, 0% reflection and 0% emission, it would appear perfectly black. It would also violate the second law of thermodynamics, though.
A: Nothing special. Just a pretty black object.
Common black object do reflect some light, therefore, they are in fact grey. On a grey scale your object would be in one end and a perfect white object (that reflects all incidents light) would have been in the opposite edge.
It is interesting to notice that by being perfectly black, no visual information should come to your eyes (other than the absence of light, obviously) and consequently it would look perfectly smooth as well.
A: Freecharly's answer is correct but it is worth noting that there is indeed a substance with properties very, very near to the hypothetical posed by the OP. It's commercial name is "Vantablack" and when one looks upon the something coated in it, the visual effect is eerie, unearthly and unsettling to say the least.
It is a coating of carbon nanotubes deposited so that they are directed normal to the coated surface. Indeed the name comes from Vertically Aligned Carbon Nanotube Arrays.  Not only does the array have an effective refractive index of very near to 1, it effectively absorbs all incident visible light. 
So nothing is reflected. This has a number of weird perceptual effects. With no reflected light, almost no information at all reaches the mind of the observer about the surface texture. The brain really is not accustomed to having no textual information about extended surfaces, so the unearthly feeling the sensation evokes has to be experienced to really understand. In particular, aluminum foil coated in Vantablack and crumpled badly still appears perfectly flat - there is no hint of surface crinkling whatsoever.
A: As we know we cannot see unless and untill the reflected light from the object comes and focuses to our Retina(Eye).
Here you said a body which is absorbing all the visible light spectrum then we will not be able to see anything.
Those who are saying BLACK let me tell you black is not a colour it appears black because it absorbs all the visible light spectrum.
Saying black is wrong and saying nothing will be visible will be technically right because to see colours we need reflected light which is not coming here.
