The void is both a thing and a place, and even more like an abstract concept than anything else. The void is both here, and everywhere else simultaneously. Nothing exists in the void, and yet everything exists. It is the veil between Heaven and Hell and Earth and Atlas, and can only be opened by meta-beings, such as angels and demons. Most mortal humans cannot survive passing through the void and only a handful of people or species are completely immune to it's impact on the physical body and the mind.
If one goes through the Void, the only description you cane give is blank, white, nothingness. There is no gravity, there is nothing to see, and it's almost blinding to those unused to it. Side effects of normal beings who go through the Void may or may not include severe vertigo, muscle fatigue, lingering blackouts, amnesia/memory loss, confusion, anxiety, depression, hallucinations, muscle spasms, difficulty breathing, decreased appetite, and death.