The Grim Reaper
is the physical Incarnation of death
; the reaper of human souls. General lore
and legend depict the Grim Reaper, or Death with a capital D, as a skeleton shrouded in a black cloak, weilding a crooked old farming scythe
which he uses to separate souls from bodies. He is also said to go about his business riding a great white horse.
While the above is generally accepted as the image of Death, there are a few points about death which many groups disagree with.
Death's Nature: Is Death good, evil, or neutral? Death is portrayed in some stories as a compassionate doctor, who just does what he has to do to relieve the pain and suffering of the dying. In other stories, he has no feeling at all, just a ghost who goes around doing his job because he is eternally damned to do so, and the other version of Death where he is a creation of Satan, who is evil and likes to reap souls just for the sake of being evil.
Death's Appointments: Does Death come personally to oversee the evicting of souls of every human being, or does he only come to certain people of importance, or whose good and evil hang in the balance and need to be carefully sorted? Does he appear visible to the victim (or patient as some would say) and what about his close ones, will they see Death, or will he be invisible? In many stories, Death only comes to take the souls of certain people of importance. In the Discworld by Terry Pratchett, Death only appears to Wizards. In Incarnations of Immortality by Piers Anthony, Death only comes to personally claim humans who are hanging in the balance between good and evil. In other versions, Death makes appointments with anyone who is alive (however this is more difficult to understand since there are literally thousands of people dying each minute).
However, the general idea is the same...Death is the collector of Souls and he is the bell-boy of the afterlife, however much more respected and feared. His power is known by everyone. And eventually, everyone also gets to know him.
"I can be cheated, but I can never be denied." Death of Discworld.
"We receive the death sentence the moment we are born" Unknown.